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What is the value of 0.5(x^2) - 1.4x - 0.7 for x = 1.4

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by aman88 » Sun Dec 16, 2012 7:34 am
IMO E
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by Brent@GMATPrepNow » Sun Dec 16, 2012 10:27 am
varun289 wrote:what is the value of 0.5(x^2) - 1.4x - 0.7 for x = 1.4 ?
(A) -0.28
(B) -0.54
(C) -0.72
(D) -1.42
(E) -1.68
If we don't trust ourselves with these kinds of calculations, we could take the following algebraic approach:

Plug in 1.4 for x to get: 0.5(1.4)(1.4) - 1.4(1.4) - 0.7
Since (0.5)(1.4) = 0.7, we get: (0.7)(1.4) - 1.4(1.4) - (0.5)(1.4)
Since each term has 1.4, combine them to get: (-1.2)(1.4)

Now observe that (-1)(1.4) = -1.4
So, (-1.2)(1.4) is considerably less than -1.4.
Only answer choice E meets this criteria, so this must be the correct answer.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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