Solve the inequality x2 + 2x > 15.
-
A.
x 5 -
B.
-5 -
C.
x 5 -
D.
x > 3 or x
Correct Answer: Option D
Explanation
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 3
i.e. x