Find the number of real values x that satisfy the equation
⌊ x ⌋ + ∣ x ∣ + ⌈ x ⌉ = 1 0 0 0 .
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Nice... (+1)
Same method, but my phone lagged and i pressed the option next to it :(
I also know that 0 real values is the answer for my previous problem, but just to make sure, so i ask on slack, then yeah you guys know it ;)
I want to ask, could x be a complex number ?
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How would we define ∣ x ∣ if x is a complex number?
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|x| is well defined in complex numbers. I think you meant to say about floor and ceiling function...:-)
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@Rishabh Jain – It is? I didn't know. How do you define ∣ x ∣ for complex numbers?
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@Hung Woei Neoh – If x = a + i b sich that a , b are real numbers then ∣ x ∣ = ∣ a + i b ∣ = a 2 + b 2
@Hung Woei Neoh – OK I thought about modulus... Obviously we cannot judge it by the definition ∣ x ∣ = x if x is positive and − x if x is negative..
Good question, probably a bit overrated though. Same method, +1
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I selected Level 3. The level was then pushed to 4
Wait, are ⌈ x ⌉ , and ⌊ x ⌋ positive for negative x?
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Nah, never. The range of ⌊ x ⌋ is ( − ∞ , − 1 ) for any negative real value of x , while ⌈ x ⌉ ranges from ( − ∞ , 0 ) for the same.
Nope. They retain the sign
Since ⌊ x ⌋ , ⌈ x ⌉ and 1 0 0 0 are all intergers, 1 0 0 0 − ⌊ x ⌋ − ⌈ x ⌉ = ∣ x ∣ is an integer too by closure and so is x . Therefore ⌊ x ⌋ = ⌈ x ⌉ = x . This simplifies the equation to ∣ x ∣ + 2 x = 1 0 0 0 . If x is positive then this becomes 3 x = 1 0 0 0 which has no integer solutions. If x is negative then it becomes x = 1 0 0 0 which is not a negative solution and thus rejected. If x = 0 then 0 = 1 0 0 0 which is obviously false. Therefore there are no solutions.
The only answer is
x
=
3
3
3
1
. The cieling and floor functions give 34 and 33. While these two and the sum are integers the absolute value function is
3
3
3
1
.
So the sum is not 1000 but
1
0
0
0
3
1
. We also know integer+integer+non integer can not add up to an integer. So no solution.
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Relevant wiki: Floor and Ceiling Functions - Problem Solving
⌊ x ⌋ + ∣ x ∣ + ⌈ x ⌉ = 1 0 0 0
For this equation, we will analyze 3 cases:
Case 1 : x is a non-integer real value
Note that for non-integer real values x , we have
We will never get an integer value result. This means that no non-integer real value x satisfies this equation.
Case 2 : x is a non-negative integer
For non-negative integers x , we have ⌊ x ⌋ = ⌈ x ⌉ = ∣ x ∣ = x . This means we have
x + x + x = 1 0 0 0 ⟹ 3 x = 1 0 0 0 ⟹ x = 3 1 0 0 0
The value of x found isn't an integer. Therefore, no non-negative integer x satisfies this equation
Case 3 : x is a negative integer.
For negative integers x , we have ⌊ x ⌋ = ⌈ x ⌉ = x and ∣ x ∣ = − x . This means we have
x − x + x = 1 0 0 0 ⟹ x = 1 0 0 0
The value of x found is non-negative. This means that no negative integer x satisfies this equation either.
From here, we can conclude that there are 0 real values x that satisfy this equation