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the rule is that if root x +root x + root x=5, and the radicals are nested and it's an infinite series, then 5=root(x+5). so, you can derive the same one step equation in the solution. Really amazing solution by the way. What level math are you learning right now?
That is a really nice solution
bhai log sidha concept jasiey ocean sey ek drop water nikalna . same concept for this and for other q of this type rootx + rootx + rootx + ........=5 using concept agey sey chod key ek x baki ko dekhen to =5 to root under jo tha uska value root under x+5 =5 ab root shifting and now x+5=25 x=20;
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bhaiya root shifting kya hota hai....uske bare me bataiye pls ....
Got the Same
Simple solution!
Thanks! Ihave new trick to share now :)
a good one
Sorry Ben I lied to you, it's not Landau. It's just some common rule.
Good explanation! \sqrt{x+sqrt(x)...}=5
I'm still no really understand !
good
Nice
Nice solution!
nice thinking
nice good thought
superb
keep it up, good job
Cognitive query, nice solution
nice and easy
woooh! i really love math
nice
amazing solution
OR simply solve it using the calculator, the answer will be approaching 20
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I agree, but as an engineer student, we are taught to find the quickest and simplest solution to any problem which is by using the calculator
généralement, si x étant un nombre réel supérieur ou égal à 1 :
{\sqrt {x+{\sqrt {x+{\sqrt {x+{\sqrt {x+\cdots }}}}}}}}={\frac {1+{\sqrt {(4\,x+1)}}}{2}}
Alors :
{\frac {1+{\sqrt {(4\,x+1)}}}{2}}=5
x=80/4=20 .
Very easy........................
good
awesome solution.
Let LHS expression=a. Squaring both sides yield
x + a = 25 -> x + 5 = 25 -> x = 20
the best solution !!
But this will only give us approx value
My goodness, I am getting slow, thanks for this. Need to practice my math skills to achieve my goal on being a math teacher.
thanks for reminding me i am slow...
We should get this to 20 upvotes
how i can write sqrt(x) symbolically please help.
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You use LaTeX. In order to start LaTeX, you write \ ( without a space in between, and then \ ) to end it. The way to make a square root sign in LaTeX is \sqrt{...}
Do you know what Landau's algorithm is?
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Isn't Landau's algorithm used for denesting finite radicals of radicals? This is an infinite radical, and so I think that that doesn't apply here, though I don't know much about Landau's algorithm.
If someone could please highlight X and say, "Here it is," that would make me happy
nice try
good one
what level is this question
clever approach, i solved it using guess and check
x + x + x + . . . . = 5 .....(i)
On squaring both sides, we get,
x + x + x + x + . . . . = 2 5
x + 5 = 2 5 [From (i)]
x = 2 0
good
Did you use Landau's Theorem?
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No, I just squared both sides of the original equation and then substituted the value of x + x + x + . . . with the value from original equation to get the value of x = 2 0
i solved this q in my syllabus book
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Hello! you have told that you have solved this query in your syllabus book.I am a medical student and have no expertise in the field of mathematics. For the preparation of aptitude test will you kindly tell me that book and as well some others(in case if you know), so that I will be very humble to you.
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reply must I am in dire need of suggestions as test is looming ahead me
We can consider a sequence as a 1 = x , a 2 = x + x , a 3 = x + x + x , . . . . Clearly for any n > 1 , a n + 1 = x + a n that implies , a n + 1 2 = x + a n We are given that n → ∞ lim a n = 5 . So we take the both hand limits and get, x = n → ∞ lim a n + 1 2 − n → ∞ lim a n = 5 2 − 5 = 2 0
Thanks for writing this answer, I really want to understand how the question was solved this way. Would you mind answer a few difficulties that I have in understanding this answer?
1) for n > 1, a(n + 1) = sqrt(x + an) - I just don't understand this,
2) Limit of a(n) = 5, a(n+1) = 5^2? I just get how! And in the end, why did you subtract the limit, was there any logical connection of sorts?
Sorry, but sometimes I really am slow in understanding Maths!
nice one~~
different thinking..
very nice
thank you :D you made me understand ^_^
Why are you trying to eat around your head, still you can directly eat
i think its very easy with limits
Great solution. So elegant. Harder math applied simply becomes truly elegant and intelligible any solution.
Let $$(\sqrt ( x+\sqrt (x+ \sqrt (x+... \infty)=a ....(i) $$ Again $$(\sqrt ( x+\sqrt (x+ \sqrt (x+... \infty)=5 ....(ii) $$ Hence, $$a=5$$ Squaring on both sides of (ii): $$x+ (\sqrt ( x+\sqrt (x+ \sqrt (x+... \infty)=25$$ $$\Rightarrow x+a=25$$ $$\Rightarrow x=25-5$$ $$\Rightarrow x=20$$
Good xplanation.,thanks
\sqrt{x}
nice
Great explanation.
great
We have: \begin{align} \sqrt{x + \sqrt{x + \sqrt{x + \dots}}} &= 5 \\ x + \sqrt{x + \sqrt{x + \dots}} &= 25 \\ x + 5 &= 25 \\ x &= \fbox{20} \end{align}
x + x + x + . . . = 5
x + 5 = 5
x + 5 = 2 5
x = 2 0
Given, x + x + x + . . . = 5 .......... (i)
Here, there are infinite x terms inside the square roots.
Square both sides,
x + x + x + x + . . . = 2 5 .......... (ii)
Here, there are one less than infinite x 's, which is same as infinite x terms in the square roots.
Therefore, using (i), we can write (ii) as
x + 5 = 2 5
x = 2 0
That's the answer!
Squaring on both sides to the equation then we get x + x + x + … = 2 5 Then substituting x + x + x + … = 5 into the equation above, we will get x + 5 = 2 5 . Finally we get x = 2 0
√x+√x+√++........=√x+5=5(because it is an infinite series) squaring on both sides, x+5=25, x=20
Square both sides and subtract x from both sides:
x + x + x + . . . = 2 5
x + x + . . . = 2 5 − x
Then substitute in the original equation, and you have
5 = 2 5 − x
x = 2 0 .
x + x + x + . . . . . . = 5 or x + 5 = 5 or x + 5 = 2 5 or x = 2 0
If I take the geometric series approach, then the powers of x are 1/2, 1/4, 1/8, and the series sums to 1.
Then, x = 5
This is different from the "other / correct" answer.
Why does the geometric series approach give a different answer, and which one is correct?
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Ok. I got it. I cant apply a geometric series here becuase of the plus signs.
Let x + . . . . . = a. Then, a = 5
Therefore, x + a = 5
Thus, x + a = 25
But a =5
Therefore, x = 20
nice method!
The question is very easy,even though it looks tough n + n + n + … = 5 And as the concept for such question is to use the formula x = 2 1 + 4 n + 1 Hence we do... 2 1 + 4 n + 1 = 5 We multiply RHS and LHS by 2 1 + 4 n + 1 = 1 0 Then we subtract 1 from RHS and LHS 4 n + 1 = 9 Squaring both the sides 4 n + 1 = 8 1 Subtracting 1 from both sides 4 n = 8 0 Dividing both sides with 4 n = 2 0
That 8 legged cat made my little brother laugh out of his wits....! Awesome question and the apt (octapede... :-) )image'-.....!
I had no idea what I was doing so I first converted it to X 1 / 2 + X 1 / 4 + X 1 / 8 . . . = 5
Then I realized that X + X 1 / 2 + X 1 / 4 + X 1 / 8 . . . = 5 2
and that X + X 1 / 2 + X 1 / 4 + X 1 / 8 . . . = 5 + X
So I just did 2 5 = X + 5
Let y = √ x + √ x + √ x + √ x +……………….. Now according the question y = 5 y^2 = 25 = x + √ x + √ x + √ x +……………….. or we can say y^2 = y + x 25 = 5 + x or x = 20
root inside root go to infinite times then we assume , if we hold a first root x and until go to 5 because this turns TO INFINITE. let's simplfies sqrt(x+5)=5; x+5=25; x=20;
\sqrt{x}+\sqrt{x}+\sqrt{x}..........=5 \sqrt{x}+5 =5 Squaring bothsides, x+5=23 Therefore,x=20
In the equation, keep the roots other than the value of the first 'x' as 5. Solving, root of (x+5)=5 Squaring, we get, x+5=25.So,x=20.
√(x +√(x + √(x + . . . . .))) = 5 ---------(i) Squaring both sides, we get x +√(x + √(x + . . . . .)) = 25 or, x + 5 = 25 [from (i)] So, x = 25 – 5 = 20
square on both sides you will get
x + sqrt(x(sqrt(xsqrt(x)))..= 25 , Now the value of sqrt(x(sqrt(xsqrt(x))) = 5 from given question. So replace it with 5.
you will get x + 5 = 25 , which implies x = 20
Solution: √(x+√(x+√(x+⋯)))=5 ≫√(x+5)=5 [ as √(x+√(x+√(x+⋯)))=5 ] ≫x+5=25 ∴x=20
Square the expression on both the sides. One x will come out. Replace the remaining x's with 5 as they continue till infinite. You will have x + 5 = 2 5 . Hence x = 2 0 .
√(x+√(x+√(x+⋯)) ) =5 〖(√(x+√(x+√(x+⋯)) ) )〗^2=5^2 x+√(x+√(x+⋯)) =25 As we know that √(x+√(x+√(x+⋯)) ) =5 x+5=25 x=25-5 x=20
y = sqrt(x + sqrt(x + sqrt(x + ….)))
y2 = x + sqrt(x + sqrt(x + sqrt(x + ….)))
y2 = x + y
Now, we have y = 5
52 = x + 5
25 = x + 5
x = 20
GIVEN THAT,
√(x+√(x+√(x+⋯)=5
SO WE CAN WRITE THAT,
√(x+5)=5
NOW,
x+5=5^2
x+5=25
THEREFORE, x=25-5=20
squaring both sides, then put \sqrt{x}+\sqrt{x}+....+5 then it will give us x=20 Ans
Since infinite number of square roots are there, we approach the prob like this : 1. Square on both sides 2 . x + infinitely long term = 25 3 . Since, infinitely long term = 5 4 . x + 5 = 25 5 . x = 20
The above problem can be written as sqrt{x+5} = 5; or, x+5 = 25; x= 25-5; or x = 20
Squaring both sides, we get x+ \sqrt{x+\sqrt{x+...}} = 25. Using the given equation, x+5=25. Hence, x=20.
at first consider the whole expression to be y=5 next ,square both sides..we get. x+y=25 since y=5 so x=20
\sqrt x+5=5
squaring both side
x+5=25
x=20
given root of(x+<x+.....)=5 implies root of(x+5)=5 implies x+5=25 then we get x=20
square the both side of the given equation and then we get that x+5 = 5^2 =25 implies that x=20
Based on my analysis, on every radicand must be equal to 25 to become 5, if you subtract 5 from 25 it become 20, so that your x is 20.
squaring both sides: x+5=25; x=20
let the left side of the equation be =a squaring on both sides we get x+a=25 as a=5 x=20
√(x+√(x+√(x+⋯)) ) = 5
[√x+√(x+√(x+⋯)) ]^2= [5]^2
Let 5 be them:
x+(5)=25 x=25-5 x=20
squaring both sides we get: x +y=25 (y=l.h.s.=5 which is the initial eqn.) x+5=25 x=20
Hopefully this does not get lost among the comments. Evaluate sqrt{x+sqrt{x+sqrt{x+...= 1 what is x? Just don't tell me you get x=0. If so I would sure like an explanation.
Here, x + x + . . . . . + . . . . . =5
Hence We have,
x + 5 =5
So, x+5=25
Or, x=20
The limit of x + x + x + . . . is 5
Hence, we have
x + 5 = 5 .
Solving for x gives x = 2 0
Could you please elaborate on how you solved the Limit?
sqrt(x + sqrt(...))=5 x+sqrt(...)=25 5=sqrt(...) x+sqrt(...)-sqrt(...)=25-5=20
it is infinitely long , so if we take out one x , it would not affect the whole series as the series is infinitely long. so the remaining series becomes exactly the same series which is equal to 5.
so therefore
5= Vx+5 squaring and solving , we get x=20
( x + ( x + ( x + . . . ) ) ) = 5 ⇔ ( x + 5 ) = 5 ⇔ x + 5 = 2 5 ⇔ x = 2 0
Notice that x + 5 = 5 . Squaring both sides, we get x + 5 = 2 5 so x = 2 0 .
tke infinite =5 .. what we left is x+5=5^2 ; 20
5=sqrt(x+5) => 25=x+5=> 20=x.
We define the expression with roots to be S -> S=5. By squaring both sides we get x+S=25, and thus x=25-5=20
square both sides... Now the eqn becomes x+5=25 ( putting given eqn again) So, x=20
square both sides 25=x+5
Let x + x + x + ⋯ denote the infinite nested radicals.
We have x + x + x + ⋯ = 5 ⇒ x + x + x + x + ⋯ = 5 2 . But because x + x + x + ⋯ = 5 , we can substitue it back and find that x + 5 = 2 5 ⇒ x = 2 0 .
Yup you got the trick
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Squaring both sides we get,
x + x + x + … = 2 5
We know from the original equation that x + x + x + … = 5 , so we substitute.
x + 5 = 2 5 ⇒ x = 2 0