MATHEMATICS

JAMB 2014 - Question 21

Mathematics 2014 JAMB Past Questions - Question 21: A binary operation *is defined by x*y=xy .if x*2=12-x,find the possible values of x.

A binary operation *is defined by x*y=xy .if x*2=12-x,find the possible values of x.
A:
B:
C:
D:
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Correct Answer

C

Explanation

x * y = xyx * 2 = 12 - xThus by comparison,x = x, y = 2But x * y = x * 2xy = 12 - xx2 = 12 - xx2 + x - 12 = 0x2 + 4x - 3x - 12 = 0x(x + 4) - 3(x + 4) = 0(x - 3)(x + 4) = 0x - 3 = 0 or x + 4 = 0So x = 3 or x = -4