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09 Aug 2017, 08:36
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If a+b=x and a-b= y , then 2ab=?
A. (x^2-y^2)/2
B. (y^2-x^2)/2
C. x-y/2
D. 2xy
E. (x^2+y^2)/2
A. (x^2-y^2)/2
B. (y^2-x^2)/2
C. x-y/2
D. 2xy
E. (x^2+y^2)/2
09 Aug 2017, 09:06
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Given:
a+b=x -> (1)
a-b= y -> (2)
(1)+(2) => \(x+y = 2a\) ->(3)
(1)-(2) => \(x-y = 2b\) ->(4)
Multplying (3) and (4),we get
\(4ab = (x-y)(x+y) = x^2 - y^2\)
Therefore, \(2ab = \frac{x^2 - y^2}{2}\)(Option A)
a+b=x -> (1)
a-b= y -> (2)
(1)+(2) => \(x+y = 2a\) ->(3)
(1)-(2) => \(x-y = 2b\) ->(4)
Multplying (3) and (4),we get
\(4ab = (x-y)(x+y) = x^2 - y^2\)
Therefore, \(2ab = \frac{x^2 - y^2}{2}\)(Option A)
09 Aug 2017, 10:45
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Skywalker18
If a+b=x and a-b= y , then 2ab=?
A. (x^2-y^2)/2
B. (y^2-x^2)/2
C. x-y/2
D. 2xy
E. (x^2+y^2)/2
A. (x^2-y^2)/2
B. (y^2-x^2)/2
C. x-y/2
D. 2xy
E. (x^2+y^2)/2
This is basically the same question as the following:
https://gmatclub.com/forum/if-a-b-x-and ... 34848.html
https://gmatclub.com/forum/if-a-b-x-and ... 54248.html
