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WAEC Further Mathematics 2022 Question 6

Question 6

Functions

The functions f: x → 2x2 + 3x − 7 and g: x → 5x2 + 7x − 6 are defined on the set of real numbers, R. Find the values of x for which 3f(x) = g(x).

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

Answer: C (x = 3 or −5)

Explanation

6x² + 9x − 21 = 5x² + 7x − 6 gives x² + 2x − 15 = 0, (x + 5)(x − 3) = 0, so x = 3 or −5.