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JAMB UTME - Mathematics - 2008

Tambaya 1 Rahoto

The solution of the quadratic inequality \(x^2 + x - 12 \ge 0\) is

Bayanin Amsa
(x2 + x - 12)  ≥  0 , (x - 3)(x + 4)  ≥  0
For the condition to hold, each of (x - 3) and (x + 4) must be of the same sign
.i.e. x - 3  ≥  0 and x + 4  ≥  0
or x - 3 ≤  0 and x + 4  ≤  0
when x  ≥  3, the condition is satisfied
when x  ≥  -4, the condition is not satisfied.
when x  ≤  3, the condition is not satisfied
when x  ≤  -4 , the condition is not satisfied. Thus, the solution of the inequality is x  ≥  3 or x  ≤  -4 ,