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WAEC Further Mathematics 2009 Question 1

Question 1

Polynomials

Solve x2 − 2x − 8 > 0

  1. A.x < −2 or x > 4
  2. B.x < −4 or x > 2
  3. C.−2 < x < 4
  4. D.−4 < x < 2
Show the answer and explanation

Answer: A (x < −2 or x > 4)

Explanation

x2 − 2x − 8 = (x + 2)(x − 4). The product is positive outside the roots, so x < −2 or x > 4.