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# What is the value of x^4y^2 - x^4y^2 ?

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Math Expert
Joined: 02 Sep 2009
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What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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24 Mar 2015, 03:48
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Difficulty:

45% (medium)

Question Stats:

69% (01:31) correct 31% (01:56) wrong based on 130 sessions

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What is the value of x^4y^2 - x^4/y^2 ?

(1) x = 2y

(2) y = 1

Kudos for a correct solution.

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Joined: 07 Aug 2011
Posts: 529
GMAT 1: 630 Q49 V27
Re: What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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24 Mar 2015, 05:47
Bunuel wrote:
What is the value of x^4y^2 - x^4/y^2 ?

(1) x = 2y

(2) y = 1

Kudos for a correct solution.

(1) x = 2y
on substituting x=2y into $$x^4y^2 - x^4/y^2$$ we will get an expression in Y . Not sufficient.

(2) At y = 1
$$x^4y^2 - x^4/y^2$$ = 0 Sufficient. answer :B
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What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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24 Mar 2015, 05:52
x^4y^2 - x^4/y^2 ?

written in this form, we get
x^(4y^2) which is x^16y
(1) doesn't tell much
(2) from x^16y we substract x^4, since y^2 =1
I guess something is missing here..
it is not clear whether (x^4)*(y^2) or that 4y^2 is the exponent of x.
if it is the first option, then the answer is B
if it is the second one, then the answer is E.
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Re: What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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24 Mar 2015, 11:16
1
On further simplification of the problem we get , x^(8y) - x^(8/y)

St 1 gives a unkown variable. Not Sufficient.
St 2 solves the unknown. Sufficient.

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Re: What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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24 Mar 2015, 18:38
1
Bunuel wrote:
What is the value of x^4y^2 - x^4/y^2 ?

(1) x = 2y

(2) y = 1

Kudos for a correct solution.

Statement 1:
after substituting 2y for x, we are still left with y
Insufficient

Statement 2:
when y=1, the expression equates to 0
Sufficient

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Posts: 7334
Re: What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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24 Mar 2015, 20:02
FightToSurvive wrote:
On further simplification of the problem we get , x^(8y) - x^(8/y)

St 1 gives a unkown variable. Not Sufficient.
St 2 solves the unknown. Sufficient.

hi,
you will have to check on the equation you get after simplifying...
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Re: What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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24 Mar 2015, 23:27
1
X^4Y^2-x^4/Y^2

1. X=2Y; substituting values equation will be in one variable 2Y^4Y^2-2Y^4/Y^2, but value of y is still unknown, not sufficient

2. y=1, X^4-X^4=0; sufficient

Thanks,
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Posts: 52905
Re: What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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30 Mar 2015, 03:34
Bunuel wrote:
What is the value of x^4y^2 - x^4/y^2 ?

(1) x = 2y

(2) y = 1

Kudos for a correct solution.

MAGOOSH OFFICIAL SOLUTION:
Attachment:

evaluationwexpo_explanation.png [ 34.72 KiB | Viewed 1461 times ]

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What is the value of x^4y^2 - x^4y^2 ?  [#permalink]

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22 Oct 2018, 11:42
Bunuel wrote:
What is the value of x^4y^2 - x^4/y^2 ?

(1) x = 2y

(2) y = 1

$$?\,\,\,\, = \,\,\,\,{x^4}{y^2} - {{{x^4}} \over {{y^2}}}\,\,\,\, = \,\,\,\,{x^4}\left( {{y^2} - {1 \over {{y^2}}}} \right)$$

$$\left( 1 \right)\,\,x = 2y\,\,\,\,\left\{ \matrix{ \,{\rm{Take}}\,\,\left( {x,y} \right) = \left( {2,1} \right)\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,? = \,\,\,{2^{\,4}}\left( {1 - 1} \right) = 0 \hfill \cr \,{\rm{Take}}\,\,\left( {x,y} \right) = \left( {4,2} \right)\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,? = \,\,\,{4^{\,4}}\left( {4 - {1 \over 4}} \right) \ne 0\,\, \hfill \cr} \right.$$

$$\left( 2 \right)\,\,y = 1\,\,\,\,\, \Rightarrow \,\,\,\,\,\,?\,\, = \,\,{x^4} \cdot \left( {1 - {1 \over 1}} \right)\,\, = \,\,0\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{\rm{SUFF}}.\,\,\,\,\,\,$$

This solution follows the notations and rationale taught in the GMATH method.

Regards,
Fabio.
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What is the value of x^4y^2 - x^4y^2 ?   [#permalink] 22 Oct 2018, 11:42
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