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The solution of the quadratic inequality x2 x -... - JAMB Mathematics 2007 Question

The solution of the quadratic inequality (x2 + x - 12) \(\geq\) 0 is
A
x \(\geq\) 3 or x \(\geq\) -4
B
x \(\leq\) 3 or x \(\leq\) -4
C
x \(\geq\) 3 or x \(\leq\) -4
D
x \(\geq\) -3 or x \(\leq\) 4
correct option: c

(x2 + x - 12) (\geq) 0 , (x - 3)(x + 4) (\geq) 0

For the condition to hold, each of (x - 3) and (x + 4) must be of the same sign

.i.e. x - 3 (\geq) 0 and x + 4 (\geq) 0

or x - 3(\leq) 0 and x + 4 (\leq) 0

when x (\geq) 3, the condition is satisfied

when x (\geq) -4, the condition is not satisfied.

when x (\leq) 3, the condition is not satisfied

when x (\leq) -4 , the condition is not satisfied. Thus, the solution of the inequality is x (\geq) 3 or x (\leq) -4 ,

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