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Inequality?? DID OG10 mess this one up?

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Inequality?? DID OG10 mess this one up?

by oquiella » Sat Oct 10, 2015 5:19 am
If 4-x/2+x = x, what is the value of x^2 + 3x-4?

A. -4
B. -1
C. 0
D. 1
E. 2


I plugged every answer in the first equation and got D. But OG is sayong it's C. 0. Which is true but the question asked for the value of the second question after solving the first. X in the first equation will not equal 0 if I substitute x for ) in the first equation.
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by GMATGuruNY » Sat Oct 10, 2015 6:22 am
oquiella wrote:If 4-x/2+x = x, what is the value of x^2 + 3x-4?

A. -4
B. -1
C. 0
D. 1
E. 2
(4-x)/(2+x) = x

4-x = x(2+x)

4-x = 2x + x²

0 = 2x + x² - 4 + x

0 = x² + 3x - 4.

Question stem: What is the value of x² + 3x - 4?
According to the resulting equation above, x² + 3x - 4 = 0.

The correct answer is C.
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by theCEO » Sat Oct 10, 2015 7:29 am
Very important to copy the question exactly as it is typed!
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by [email protected] » Sat Oct 10, 2015 8:36 am
Hi oquiella,

The question is NOT asking for the value of X, so plugging the 5 answer choices into the first equation is NOT going to get you the correct answer (the question ask for the value of X^2 + 3X - 4). Knowing that X = 1 though, you're one step away from answering the question (and you'll find that the answer is 0.)

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