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

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Manager
Joined: 09 Dec 2006
Posts: 96

Kudos [?]: 41 [0], given: 0

if xy+z=x(y+z), which of the following must be true? a.  [#permalink]

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19 Aug 2007, 09:45
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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 and y=0
e. x=1 and z=0

Kudos [?]: 41 [0], given: 0

Senior Manager
Joined: 06 Mar 2006
Posts: 489

Kudos [?]: 276 [0], given: 1

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19 Aug 2007, 09:51
well, xy+z=x(y+z)
xy+z=xy+xz
z-xz=0
z(1-x)=0
z=0; x=1

Kudos [?]: 276 [0], given: 1

VP
Joined: 09 Jul 2007
Posts: 1098

Kudos [?]: 144 [0], given: 0

Location: London

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19 Aug 2007, 10:00
Piter wrote:
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 and y=0
e. x=1 and z=0

It looks complicated, only thing u need is simplifying the equation.
xy+z=x(y+z)
xy+z=xy+xz
xy+z-xy-xz=0
z-xz=0
z(1-x)=0
z=0 and x=1

E

Kudos [?]: 144 [0], given: 0

Intern
Joined: 01 Aug 2007
Posts: 38

Kudos [?]: [0], given: 0

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19 Aug 2007, 10:55
I believe this question is worded incorrectly... some of the answer choices should say OR not AND.

But, yes, straight E on this one.

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19 Aug 2007, 10:55
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