ammuseeru wrote:

Could you help me with following question.

If \(a^2\) – \(ab\) = \(2b^2\), which of the following could be b/a ?

I. \(1/2\)

II. \(2\)

III. \(-1\)

(A) I only

(B) II only

(C) I and II

(D) I and III

(E) II and III

HI..

If you are seeing an equation in terms of variables and value asked in terms of fraction, try dividing the equation by the variable in denominator..here divide equation \(a^2\) – \(ab\) = \(2b^2\) by \(a^2..\)..

so \(\frac{a^2-ab}{a^2}=\frac{2b^2}{a^2}.......... 1-\frac{b}{a}=2*\frac{b}{a}^2\)..

here you can do two things ..

(A) substitute the given values ..\(1-\frac{b}{a}=2*\frac{b}{a}^2\)..

1) 1/2..

\(1-\frac{1}{2}=2*\frac{1}{2}^2........1-1/2=1/2\)...YES

2) 2..

\(1-2=2*2^2\).....No

3) -1

\(1-(-1)=2*(-1)^2....1+1=2\).....YES

so I and III

D

(B) solve ..\(1-\frac{b}{a}=2*\frac{b}{a}^2\)..

let b/a = x..

so \(1-x=2x^2.....2x^2+x-1=0....(2x-1)(x+1)=0\)..

so x=1/2 or x=-1

D

_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372

2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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