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If xy is different from zero

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If xy is different from zero [#permalink] New post 22 Mar 2018, 03:07
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Question Stats:

81% (00:51) correct 18% (00:20) wrong based on 16 sessions
If \(xy \neq 0\), \(\frac{x - 1}{xy} =\)

(A) \(\frac{1}{x} - \frac{1}{xy}\)

(B) \(\frac{x}{y} - \frac{1}{xy}\)

(C) \(\frac{1}{y} - x\)

(D) \(\frac{1}{y} - \frac{1}{xy}\)

(E) \(\frac{1}{xy} - \frac{1}{y}\)
[Reveal] Spoiler: OA

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Re: If xy is different from zero [#permalink] New post 02 Apr 2018, 18:03
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Firstly, the xy≠0 part here isn't important. It's merely to satisfy any math nerds out there who would protest that if xy = 0, this question is undefined. Nerds!

Secondly, let's solve this. When you have a fraction with terms being added or subtracted in the denominator, a good thought is to split it into two fractions. Thus:

x-1
xy

can be split into
x - 1
xy xy

which simplifies to
1 - 1
y xy

This leads us to answer choice D.

METHOD TWO: Another way to solve this problem, or almost any other problem with variables in the answer choices, would be to pick a couple of values for x and y, for example 2 and 3, respectively, and plug them into the original equation. This results in a value of 1/6. Then plug 2 and 3 into every answer you see, and you will find that only answer choice D results in a value of 1/6. Thus, only D can be the correct answer.
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Re: If xy is different from zero [#permalink] New post 02 May 2018, 07:41
Expert's post
Carcass wrote:
If \(xy \neq 0\), \(\frac{x - 1}{xy} =\)

(A) \(\frac{1}{x} - \frac{1}{xy}\)

(B) \(\frac{x}{y} - \frac{1}{xy}\)

(C) \(\frac{1}{y} - x\)

(D) \(\frac{1}{y} - \frac{1}{xy}\)

(E) \(\frac{1}{xy} - \frac{1}{y}\)


----------ASIDE-------------------
The GRE loves to test your knowledge of the following identities:

\(\frac{a + b}{c} = \frac{a}{c} + \frac{b}{c}\)

\(\frac{a - b}{c} = \frac{a}{c} - \frac{b}{c}\)

---ONTO THE QUESTION!----------------------------------------

So we can write: \(\frac{x - 1}{xy} = \frac{x}{xy} - \frac{1}{xy}\)

Simplify first fraction to get: \(= \frac{1}{y} - \frac{1}{xy}\)


Answer: D

Cheers,
Brent
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Re: If xy is different from zero [#permalink] New post 02 May 2018, 11:37
the way I did this was basically workout each option and also workout the equation in the question
Re: If xy is different from zero   [#permalink] 02 May 2018, 11:37
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