Question on: JAMB Mathematics - 2011
Solve the inequality x2 + 2x > 15.
A
x < -3 or x > 5
B
-5 < x < 3
C
x < 3 or x > 5
D
x > 3 or x < -5
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Correct Option: D
x2 + 2x > 15
x2 + 2x - 15 > 0
(x2 + 5x) - (3x - 15) > 0
x(x + 5) - 3(x + 5) >0
(x - 3)(x + 5) > 0
therefore, x = 3 or -5
then x < -5 or x > 3
i.e. x< 3 or x < -5
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