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If x>0, does f(x^2)=f(x)^2?

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If x>0, does f(x^2)=f(x)^2? [#permalink]

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New post 07 Mar 2016, 03:25
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A
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C
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E

Difficulty:

  35% (medium)

Question Stats:

61% (00:47) correct 39% (00:48) wrong based on 360 sessions

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If x>0, does f(x^2)=f(x)^2? [#permalink]

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New post 07 Mar 2016, 05:16
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Bunuel wrote:
If x>0, does f(x^2)=f(x)^2?

(1) f(x)=√x
(2) x=9


Question : Is f(x^2)=f(x)^2?

Statement 1: f(x)=√x
f(x^2)=√(x^2) = x
f(x)^2 = (√x)^2 = x

since x is positive so both quantities will be equal hence
SUFFICIENT

Statement 2:x=9
We don't have the definition of f(x) hence,
NOT SUFFICIENT

Answer: Option A
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Re: If x>0, does f(x^2)=f(x)^2? [#permalink]

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New post 31 May 2016, 23:08
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Hi - I see what GMATInsights says regarding why (2) is wrong, but I don't know how to put it in my notes. Is the explanation that in order for a variable to go into a function that function must be defined as is the case in (1)? I initially just put 9 into the function
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Re: If x>0, does f(x^2)=f(x)^2? [#permalink]

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New post 31 Jul 2016, 14:40
Bunuel,

Can you post your solution? I saw the OE but I was not very satisfied with it.
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Re: If x>0, does f(x^2)=f(x)^2? [#permalink]

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New post 01 Aug 2016, 01:28
TheLostBear wrote:
Bunuel,

Can you post your solution? I saw the OE but I was not very satisfied with it.


My solution won't be much different from this one: if-x-0-does-f-x-2-f-x-214483.html#p1655449 Can you please tell me what is confusing there? Thank you.
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Re: If x>0, does f(x^2)=f(x)^2? [#permalink]

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New post 30 Aug 2016, 06:10
ISn't sqrt(x2) = |x|
I know Sqrt(x) is positive!!
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If x>0, does f(x^2)=f(x)^2? [#permalink]

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New post 28 Apr 2018, 04:58
nahid78 wrote:
If x>0, does f(x^2)=f(x)^2?

(1) f(x) = √x
(2) x=9

Please solve in details.


Question : does f(x^2)=f(x)^2?

Statement 1:f(x) = √x

i.e. f(x)^2 = (√x)^2 = x

and i.e. f(x^2) = √(x^2) = x

i.e. f(x^2)=f(x)^2

SUFFICIENT


Statement 2:x=9

But we do NOT have the function to solve and check what question expects us to check hence

NOT SUFFICIENT


Answer: option A

nahid78 : Please post DS question in DS forum

Bunuel : Please shift the question in DS forum
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If x>0, does f(x^2)=f(x)^2?   [#permalink] 28 Apr 2018, 04:58
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