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BlindVision: Master | Next Rank: 500 Posts; Posts: 253; Joined: Fri Dec 26, 2008 8:39 pm; Thanked: 8 times; Followed by:1 members

by BlindVision » Sat Jul 23, 2011 1:36 pm

If a = 1 and b = -2, then (2a^2 + b)(x + y) + (a + b)(x - y) =

A) 0

B) 2x

C) y - x

D) x - y

E) x + y

OA = C

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Source: Beat The GMAT — Problem Solving | Sat Jul 23, 2011 1:36 pm

winniethepooh: Master | Next Rank: 500 Posts; Posts: 370; Joined: Sat Jun 11, 2011 8:50 pm; Location: Arlington, MA.; Thanked: 27 times; Followed by:2 members

by winniethepooh » Sat Jul 23, 2011 2:55 pm

Substituting the values in the equation we get.
=[2*1^2 + (-2)](x+y) + [1+(-2)](x-y)
=(2-2)(x+y) + (-1)(x-y)
= 0 + -x+y
= y-x.

Hence , C

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