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WAEC Further Mathematics 2023 Question 36

Question 36

Polynomials

If m and (m + 4) are the roots of 4x2 − 4x − 15 = 0, find the equation whose roots are 2m and (2m + 8).

  1. A.x2 + 8x + 15 = 0
  2. B.x2 − 8x − 15 = 0
  3. C.x2 + 2x + 15 = 0
  4. D.x2 − 2x − 15 = 0
Show the answer and explanation

Answer: D (x2 − 2x − 15 = 0)

Explanation

The sum of the roots is 1, so 2m + 4 = 1 and m = −3/2. New roots −3 and 5: sum 2, product −15, giving x² − 2x − 15 = 0.