GMAT PREP QUESTION...

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dferm: Master | Next Rank: 500 Posts; Posts: 446; Joined: Thu Jul 26, 2007 1:07 pm; Thanked: 6 times

by dferm » Wed Apr 23, 2008 8:22 am

If xy+z=x(y+z), which of the following must be true?

A. x=0 and z=0
B. x=1 and y=1
C. y=1 and z=0
D. x=1 or y=0
E. x=1 or z=0

Please explain...

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Source: Beat The GMAT — Problem Solving | Wed Apr 23, 2008 8:22 am

hakyology: Senior | Next Rank: 100 Posts; Posts: 66; Joined: Tue Jun 05, 2007 1:39 pm; Thanked: 1 times

answer

by hakyology » Wed Apr 23, 2008 12:10 pm

xy+z=x(y+z)
xy+z=xy+xz
xz=z
xz-z=0
z(x-1)=0
therefore,
z=0 or x=1

answer:e

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