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If y = x2 - x - 12, find the range of values of x fo...

If y = x2 - x - 12, find the range of values of x for which y 0

A.

x < -3 0r x > 4

B.

x -3 or x 4

C.

-3 < x 4

D.

-3 x 4

Correct answer is B

y = x2 - x - 12
= (x - 4)(x + 3)
∴ x = 4 or x = -3
Checking the cases for y 0
We check values on the range x - 4 0; x + 3 0; x - 4 0 and x + 3 0 for the range which satisfies the inequality x2 - x - 12 0.

We find that the inequality is satisfied on the range x -3 and x 4.