If (2x + 1)^2 = 100, then which one of the following COULD equal x ?

(A) –11/2

(B) –9/2

(C) 11/2

(D) 13/2

(E) 17/2

(2x+1)^2=100

Either 2x+1=10 => 2x=9 => x=9/2
Or 2x+1=-10 => 2x=-11 => x=-11/2

Answer A

Hi vikasp99,

This question asks which of the 5 answers COULD be the solution to the given equation. When a question 'hints' that there's more than one possible solution, it's likely that the "obvious" answer will not be the one that's included in the answers.

There are two numbers - that when squared - equal 100: +10 and -10.

Thus, if we were asked for BOTH solutions, then we would have to set up 2 equations:

2X + 1 = +10
2X + 1 = -10

However, it's likely that the second option will be the one that we'll need (since it's the less-obvious solution)...

2X + 1 = -10
2X = -11
X = -11/2

Final Answer:

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************