Solve the inequality \(x^2 + 2x > 15\).

  • A x <-3 or x > 5
  • B -5 < x < 3
  • C x < 5 or x >5
  • D x > 3 or x < -5
jamb 2011mathematics

The correct answer is B. -5 < x < 3

\(x^2\) + 2x > 15

\(x^2\) + 2x - 15 > 0

(\(x^2\) + 5x) - (3x - 15) > 0

x(x + 5) - 3(x + 5) >0

(x - 3)(x + 5) > 0

therefore, x = 3 or -5

i.e. x< 3 or x > -5

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