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Algebra

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Algebra

by danjuma » Mon Sep 20, 2010 10:33 am
1. If XY + Z= X(Y + Z)-which of the following must be true?

a. X=1 and Z=0 b. X=1 and Y=1 c. Y=1 and Z=0 d. X=1 or Y=1 e. X=1 or Z=0

Thanks alot.
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by niksworth » Mon Sep 20, 2010 10:43 am
XY + Z = X(Y+Z)
=> XY + Z = XY + XZ
=> XY + Z - XY - XZ = 0
=> Z - XZ = 0
=> Z(1 - X) = 0
=> Z = 0 or X = 1

Note that the question asks what must be true and not can be true.

Thus answer is E.
scio me nihil scire
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