gmatprep question

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gmatprep question

by JGaynor » Sun Apr 04, 2010 1:56 pm
I couldn't find this in the forum...

Is xy + xz = 0

1) x=0
2) y + z = 0

I know that statement is sufficient. But statement 2 could have y= -1 and z = 1 to equal zero but we don't know the value of x..??

Any insight on why statement 2 is sufficient here will be appreciated!

Thank you,

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by student22 » Sun Apr 04, 2010 2:17 pm
Factor xy + xz = 0 into x(y + z) = 0.

Statement 1:
x = 0, so 0 * (y + z) = 0. Sufficient.

Statement 2:
y + z = 0, so x * (0) = 0. Sufficient.

I hope this answers your question, when you factor the problem like this, you don't need to know the value of x for statement 2.

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by eaakbari » Sun Apr 04, 2010 8:39 pm
Stem:


xy+xz = 0
x(y+z)=0
So statement is 0 if x=0 or
y+z = 0 i.e y=-z

Statement One
Suff
So is 2nd statement

Hence D