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WAEC Further Mathematics 2011 Question 11

Question 11

Polynomials

The sum and product of the roots of a quadratic equation are 4/7 and 5/7 respectively. Find its equation.

  1. A.7x2 − 4x − 5 = 0
  2. B.7x2 − 4x + 5 = 0
  3. C.7x2 + 4x − 5 = 0
  4. D.7x2 + 4x + 5 = 0
Show the answer and explanation

Answer: B (7x2 − 4x + 5 = 0)

Explanation

The equation is x2 − (sum)x + product = 0: x2 − (4/7)x + 5/7 = 0. Multiply by 7: 7x2 − 4x + 5 = 0.