2 x − 1 = − x
Solve the above equation for real x .
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But the square root of 1 = 1 or -1 ----> so solution exists !!!
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It always follows that x 2 = ∣ x ∣ , that is, the square root of a positive number is always positive and that the square root of a negative number is imaginary.
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That construction is not valid. Ossama is correct. We are left with sqrt of 1 can be 1 or -1.... The square root function means what value(s) can you square to get the number inside the radical. The value inside the radical is 1 so what numbers can we square to get 1. The answer to that is 1 and -1.... The solution set is the reals... X=1 makes it a valid argument.... The square root of a positive number includes the positive and negative of that value as you stated with the absolute value
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@Rishi Sarkar – That is not correct. "The" square root refers to the principal root only. A number can have two square roots, but at most one principal root.
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@Whitney Clark – Whitney, can you please elaborate what you are trying to say..
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@Abhay Tiwari – "The" square root refers to one number; "a" square root could refer to as many as two (and does, when it's not a square root of zero).
@Rishi Sarkar – The square root function results only in a positive value. If 2 values were posible, then it would not be a function by definition.
Sorry but I disagree with square root of a positive number being treated as always positive. Thats not true.
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@Nikhil Dhawale – Why do you disagree? On what basis?
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@Whitney Clark – nothing in the question forces you to use "the" square root, it is not anywhere in the question. The question is a simple equation where taking into consideration the negative root makes it possible.
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@Abdelrhman Abdellatif – Yes it does, it's the square root symbol itself, which, without a plus-or-minus sign, refers to only one thing.
But if you take the power 2 for both side there will be a solution 1 which make the equation correct
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@Mohamed Attia – you are correct. I do not know why the others is making a simple equation so difficult and complex with all the bs explanation.
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@Toufil Khan – It's not BS. The square root function is a function, and only equals one thing.
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@Whitney Clark – NO, square rooting in general is not a function unless CLEARLY stating to limit its range to +ve only , -ve only or any part of only one of them
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@Abdelrhman Abdellatif – Using the square root symbol is not general, though. It doesn't mean to take any root, but only the principal root.
The square root is a function, and for it to be a function, it needs to have at most one value of f(x) assigned to each value of x. If 2 = ± 1 , then the square root is not a function.
This is standard in mathematics, just check out any book.
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again, square rooting is not a function unless limiting its range to be so
In this equation, x=1 is not a solution because it is extraneous.
The primary difference between the debate over whether or not x can be positive or negative depends on a matter of understanding convention and definition, which is why this kind of problem is difficult.
We say that x 2 = k has 2 solutions . There are two values of x which make the equation true. However, this is very different from how we obtain k . To compare with k , we must treat the square root as a function . By definition of a function, we cannot have two outputs for one input, so that is why we take the positive solution.
By plugging in values, we are guaranteed to obtain the value of x 2 to be positive. There is no ambiguity. Similarly, in order to compare the root value to k , we have to know what we are comparing, and if we do not treat the square root as a function, there will be ambiguity in what the root value is (whether it is positive or negative). Therefore, the solution is correct.
But -1 is not the square root of 1, but only a square root. The square root refers to the principal root only.
Exactly, it should be 1 as solution exists
Nope the square root of something is always |x| however if you're talking about an equation such as x^2=4 then the answer is +/- 2 but when you say simply 4^0.5 then the answer is simply 2
A valid square root is non-negative
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The principal root is non-negative. Two roots exist, but the symbol refers to the principal only.
Exactly whar I thought as well.
i agree with it!
Generally means principal square root :).
When you are given
x
2
= 1 , then x = 1 or -1
But when you are given
x
2
=1, then x=1
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This second statement is incorrect, just substitute x = -1, then it becomes sqrt (1), which is 1.
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@Siva Bathula – But 2(-1) - 1 = -3, and sqrt (-3) is imaginary.
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@Whitney Clark – You are right. I was only responding to the statement above by Preetam, sqrt(x^2) = 1, then x has to be 1 and cannot be -1.
That is not true. +/-1 are possible solutions. You still need to check which solves the original equation as stated.
Egad, the same debate is raging over in the Facebook thread. Yes, 1 has two square roots: +1 and -1. No, 1 does not refer to both of them. The square root sign refers to the principal square root only , so 1 = 1 . For those of you who disagree, consider the quadratic formula:
x = 2 a − b ± b 2 − 4 a c
The ± sign is required precisely because the radical doesn't refer to both of the square roots of the discriminant. If the radical symbol referred to both square roots of the discriminant, then the ± sign would not be necessary.
(Edited to fix a couple typos)
How do you get 1 = -1.... What is your answer for sqrt(1)... The answer for that is either +1 or -1
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@Rishi Sarkar , @Marc Vince Casimiro has already told that √ x 2 = ∣ x ∣ now let me tell you the reason of convention:
√ 4 = x
0 = x − √ 4 . now this equation will have only 1 root which is 2(positive)
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That is not the reason, as by the false 'logic' 4 can still be − 2 in which case 0 = x − 4 is still satisfied.
It is actually to do with the fact that f : x → x 2 is not a bijection and thus does not have an inverse - which many people (incorrectly) believe to be f − 1 : x → x .
Surely -2 aswell. -2 - (-2) =0
The two equations you show have different domains. The only domain restriction for the problem above is that x must be greater than or equal to 1/2..... X = 1..... Plug in x=1 into the equation and that solves the original problem...
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@Rishi Sarkar – I know it is hard to digest that x 2 =4 can be +-2 but √4 is only +2 . If you do not trust me and others you could just draw the graph using wolfram or desmos and convince yourself. @Pi Han Goh please give us the true reason of the convention. @Prasun Biswas
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@A Former Brilliant Member – By convention, we only take the positive root: 1 6 = 4 only. However x 2 = 1 6 has two roots: x = 4 , − 4 . See the difference?
That's why in quadratic formula, we have a plus minus sign: ± , else we would only be getting one root.
Note the difference in the graphs y = x and y 2 = x .
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@Pi Han Goh – Yes , I know but how to explain someone and proof it using mathematical reasoning. Is my method correct ( you can see it in my reply to Rishi Sarkar.) Thanks .
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@A Former Brilliant Member – It's just both Ossama and Rishi got their definition of square root function wrong.
When dealing with non-negative numbers in radicals:
"The square root function means what value(s) can you square to get the number inside the radical." is wrong.
It should be
"The square root function means what non-negative value can you square to get the number inside the radical."
There's a subtle difference between x 2 = 8 1 and x = 8 1 : the first equation gives two values ± 9 while the other only gives 9 .
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@Pi Han Goh – Sorry but i think square root can be positive or negative unless specifically stated to be positive. So 1 should be the correct answer
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@Prerak Sheth – Just because you want it to be true doesn't make it true. If I have rephrased the problem as 2 x − 1 = ( − x ) 2 , then x = 1 is definitely true.
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@Pi Han Goh – There are always two roots of a square root of a number, one negative and other positive. We always need to see the one that fits in the equation. One root must satisfy the equation. That root is the answer. You cannot defy maths so easily!
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@Harsh Gupta – In algebra, when we do something like square roots, there are actually two because the number of solutions is always equal to the degree of the highest exponent. Eg Square roots of 16 are 4 and -4. -4 is a root because a negative and a negative form a positive. So, taking this into consideration, when you square a number, the outcome should be positive. A negative square is imaginary. It is always a positive quantity. Now, when we do get a solution like 1 in this case by factoring, we always have to verify the root. When you introduce your own square root, you have to verify as you are potentially adding the extraneous square root. In any case, when you plug it into the equation and it doesn't work out, it is no solution.
@Harsh Gupta – Can you draw out y = x and y = − x and tell me what you see? Are they the same?
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@Pi Han Goh – That is a very naive argument. If you really want to give an example in context of this problem, check the graphs of sqrt (x) vs -sqrt (x). If you follow strict math, they will match.
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@Prerak Sheth – So you're saying that 1 9 6 = − − 1 9 6 ?
@Prerak Sheth – If we go back and use the logic of several of the other people who have commented on this thread, they have said that the square root of one is 1 or -1. This is not true. It is true that the roots of 1 are in fact 1 and -1, however, the square root is accepted to be fact as being 1. If we put 1 into the equation we end up with sqrt(1) = -1, which, according to the logic some of you are putting out there, that would be considered wrong because the correct answer for that would then be sqrt(1) = +- 1. The arguments given above are nothing more than false logic that justifies false reasonings. The correct answer for this problem is no solutions exist. An easy way to think about it is to ask, what number can you take the square root of and get a negative number? You can't. Any positive number will always give a positive square root and negative numbers give imaginary answers.
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@Billy Zottnick – a better way to settle this dispute would be to say that its just a mathematical convention to assume that the sqrt function always returns the positive root. As far as your point is concerned, why do you think that a number can't return a negative root. A better argument would've been that a square ( geometric figure) could never have a negative length side. But here, the question asks for the roots of an algebraic equation which has got nothing to do with geometry. Here, as the roots are represented on the real number line they can definitely be negative. So, its a deep blunder on your part to say that negative roots are erroneous logic. I too went for the obvious and got it wrong b'cuz I just couldn't digest the fact that unless its given that 'x' is a geometric length, how can we assume that 'x' would always be 1 & not -1. The answer is that it was a convention adopted to avoid contradictory solutions to a single problem!!!
@Billy Zottnick – your argument is circular in nature. You are saying it is true because it is true. The question is why is sqrt (1) not equal to -1 (also)? The square and square root are opposite operation. If 1 isa square of -1, then -1 by all means is a square root of 1. Whay is wrong with that?
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@Prerak Sheth – "The square and square root are opposite operation." This is where you're wrong. They are not exactly opposite operations. Read my reply to Kalesh Verma above.
@A Former Brilliant Member – u r right,actualy,only root symbol means the positive ans.before solving this prob. note that x is real,for this 2x-1greater than equal to 0,i.e x is g.t. or equal to 1/2,but in the right side it is (-x) which is thus a negative no.,but on the left side only root symbol means a positive no..this is the fallacy or fun,i think.actualy sqrt of any no. is[+-root(no.)].,only root symbol means the positive.
Wrong. sqrt(1) is 1, and not -1. A number can have two square roots, but THE square root of one is one.
Rishi I think there is solution bcoz sqr root (2x-1)=-x means 2x-1 = x^2, then X^2 - 2x +1 =0, that means (x-1)^2=0, so there is only one value of x , it's x=1, Then if we put the value of x at main equation we will get the solution as follows sqr root (2*1-1)=-1, then it's root 1 = -1, here we can solve it in two ways 1st is squaring both side it leaves 1=1, that means it has one solution, and 2nd one is only considering the sqr root of left hand side and it leaves +/-1=-1 that means it has no specific solution.
Your solution and the method finding it are inconsistent. Look at the equation x = − 1 Which, according to your definition of √ is supposed to have no solution. Square both sides: x = ( − 1 ) 2 = 1 So now you'd claim that x=1 is a solution. So your solution is inconsistent with your claim. When you square an equation, you need to check both possible signs, or you'd lose solutions. Just like for $\sqrt[3]{x}=1$ you need to use all three possible solutions. When you want to emphasize one solution you use a sign. So + 2 x − 1 = − 1 has no solutions.
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The plus sign is redundant. The square root symbol refers to the principal root only.
but isnt sqrt 1 is +/-1
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No. "Sqrt" is a function, and functions take on only one value - in this case, nonnegative values.
If the question was stated as sqrt(2x-1)=y-x then there would be no solution since it's in terms of two variables as a function. But since the y variable isn't included in this problem, it should not be treated as a function. Therefore the sqrt(2x-1) can be +/- some real number greater than or equal to 1/2. The only value that can satisfy the aforementioned equation (not function) is 1 since +/-1=-1 for the negative case. It all comes down to if it should be treated as a function or a single variable equation.
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The square root function only takes on nonnegative values. That's what the square root symbol means.
But √1 is ±1
Also, using the quadratic formula, 1 is the solution.
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You need to check back and see whether it ( x = 1 ) actually works.
X2-2x+1=0 X=1 then 1^2-2(1)+1=0 then 0=0 so answer is 1
Incorrect reasoning. Square root of 1 is 1 and -1.
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"Square root" is singular. You gave TWO answers to that singular thing.
Exactly correct. Brilliant got it completely wrong.
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Brilliant didn't get it wrong. The root symbol refers specifically to the principal root. To get both, you need to use a plus-or-minus sign.
you may want to draw the graph yourself.
http://www.wolframalpha.com/input/?i=plot+%E2%88%9A%282x-1%29+%3D+%28-x%29
There is no way to have a root at all. The Left hand side equation does not touch/intersect Right hand side equaltion at all.
Since we're trying to find real solutions for x , it follows from LHS of the given equation (by domain of real-valued square root function) that,
2 x − 1 ≥ 0 ⟹ x ≥ 2 1 … ( i )
Also, since the square root function returns non-negative value for real x in domain, it follows that RHS ≥ 0 , i.e.,
( − x ) ≥ 0 ⟹ x ≤ 0 … ( i i )
If a real x is a solution, then it must simultaneously satisfy the inequalities ( i ) and ( i i ) . But note that,
x ≤ 0 ∧ x ≥ 2 1 ⟹ x ∈ ∅
Hence, No real solution for x exists .
Note: ∅ denotes empty set.
The advantage of this method is that you don't need to solve the equation itself. You just need to examine the domain and range of the function in LHS.
Yeah! Its the fastest method for complex equations .
Square root function need not necessarily return a non-negative value in real domain. It has to return a real value in real domain. That's the only condition.
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I didn't really understand your point. Are you trying to imply that the square root function can return a negative value for some real value in domain?
Note: I have already mentioned in my solution that we're talking about the real-valued square root, not the complex one. By that, I was trying to mean that the square root function is f : R 0 + ↦ R 0 + defined by f ( x ) = x . Sorry for any ambiguity it may have created.
Note 2: R 0 + denotes the set of non-negative reals.
You are putting the same argument in a different way. The overall dogfernce between two sides is whether -1 can be a square root of 1 or not?
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I don't understand what you're trying to say! All I did in my solution was show that if a real solution exists, it must satisfy the two inequalities (which I obtained by examining domain and range of square root function) and then concluded my answer using the trivial fact that ( − ∞ , 0 ] ∩ [ 2 1 , + ∞ ) = ∅
It'd helpful if you can point out the part of my solution which seems wrong/puzzling to you.
If x is positive, the RHS is negative, which cannot be since the range of ⋅ is positive.
If x is nonpositive, the LHS is imaginary, which again cannot be since − x is real if x is real.
From the domain , we find that :
x is greater than or equal 1/2
i.e
x is positive
So
The right hand side of the given equation is negative whereas the left one is positive.
So
No solution exist
2 x − 1 = − x
Square on both sides:
⇒ ( 2 x − 1 ) 2 = ( − x ) 2
⇒ 2 x − 1 = x 2
So x = 1 .
Verifying solution:
2 × 1 − 1 = − 1
No solution exists.
A square root has only positive values, otherwise it wouldn't be a function. For those asking for x^2 = 4, the reason why that equation has 2 roots is because you don't use sqrt to solve, you have to do it like this:
x^2 = 4
x^2 - 4 =0
(x - 2)(x + 2) = 0
Hence the 2 solutions.
Thanks for clearing the misconception. Since the square root is a single valued function, it can only give one output, and it is the positive one by convention.
Good question! I made this mistake on a math test once and never made it again! :D I thought that since a root of a square had two solutions this did too, but obviously not. The only thing you need to know is that the root has only one soltion, so you cannot have a real solution of one.
Great, you might be interested in reading this wiki: does a square root have two values?
SQUARE ROOT OF A NUMBER IS NEVER NEGATIVE
The simplest explanation: No real square root can be negative, so this equation should have no solution.
Root-over something is either 0 or positive number. So 'NO SOLUTION EXISTS' is the correct answer.
Square root of any number can't be negative except complex number.
In order for the root to be real, 2x > 1. Or x > 1/2. This means -x must be negative which contradicts the principle square root (which must be positive) on the left side of the equation.
as root never gives a negative number so the x must be -ve (result of root +ve) and after solving we get +ve x which contradict the domain of x so there is no solution for this equation.
Positive Square root of any real number cannot be negative...
If we square both sides of the equation, we get:
2x -1 = (x^2)
(x^2) - 2x + 1 = 0
the LHS can be re-written as:
((x - 1)^2) = 0
Which gives x=1
This implies that:
Square root of 1 is equal to negative 1
but we know that sqrt(1) is also equal to 1
so, sqrt(1) = -1
sqrt(1) =1
this means 1 = -1
Clearly that is impossible.
So, we can conclude that there is no solution
To find real solution for x:
Analyze quantity on RHS of given equation: If x>1/2, then quantity on right hand side of the given equation is always positive.
Analyze quantity on LHS of given equation: if x>=1/2, the quantity on LHS will become negative.
Positive quantity can never be equal to a negative quantity, so no real solution exists.
If you square both sides to solve for x, you should remember the fact that [sqrt(x)]^2= |x| , not just x.
Although, for this problem, you know the domain of reals is restricted to (.5,inf).
When you solve for |2x-1|, you solve for 2x-1=x^2 (x-1)(x-1) = 0 | x=1, but clearly it isn't a valid solution because sqrt(1) =/= -1 . If sqrt(1) did in fact equal -1, then that would mean that 1^(1/2) could be a negative value.
It is true that for any positive integers a,b: a^b cannot be negative.
Solving 1-2x = x^2 leaves you with x= -1+sqrt(2) and -1-sqrt(2) (two extraneous solutions).
Neither of these values are larger than 1/2, therefore, there are 0 real solutions to the problem.
from left side 2x-1 ≥0 so x ≥1/2 1st condition from right side -x ≥0 so x ≤ 0 2nd condition from both these condition we can conclude there is no real solution.
Square root only gives positive value, 'x' must be negative. Cross check the only two negative options, i.e. -2 and -1 in L.H.S. of equation. You ll get a complex number. Hence, no solution.
Square root of any number, can't be negative.. So it has no solution..As simple as that. :)
I think that this is already obvious that root square won't be ngeative right? In exception of imaginer number which is rootsquare of -1 haha
simple.....for y to be real.... y^1/2 cannot b negative and here we cannot put any negative value of x since sq. root of negative is unreal
See my reply to to Ajay Koritala.
the square root of any number has to be positive so -x doesn't work.
− x does not necessarily means it's negative. Take x = − 1 0 0 , then − x = 1 0 0 > 0 which is clearly positive.
And the square root of any number does not need to be positive, for example take 0 or − 4 9 .
Simply enough, no real value can give a negative output, and by using the condition for a real number, 2x-1>0 or 0 If x = 1/2 , the bare minimum for the equality to hold, then the equation does not hold. However, for any values larger than 1/2, the square root of 2x-1 is ALWAYS positive. As any value larger than 1/2 is positive, it is safe to simply say that no real solution exists.
simply see that LHS is defined for x>=1/2 and RHS being output of square root(eventh root) must be non-negative=> -x>=0=>x<=0 .Upon intersection no common 'x' is possible.
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Squaring both sides and then rearranging the above equation we get
x 2 − 2 x + 1 =0 ( x − 1 ) ( x − 1 ) =0 or x=1
But after substituting the value in equation we get
1=-1 which is not possible hence the above equation has no solution.