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WAEC Further Mathematics 2008 Question 2

Question 2

Polynomials

Find the range of values of x for which 2x2 + 7x − 15 > 0

  1. A.x < −3/2 or x > 5
  2. B.x < −5 or x > 3/2
  3. C.−3/2 < x < 5
  4. D.−5 < x < 3/2
Show the answer and explanation

Answer: B (x < −5 or x > 3/2)

Explanation

Factorise: (2x − 3)(x + 5) > 0. The product is positive outside the roots −5 and 3/2, so x < −5 or x > 3/2.