\(f(x) = p + qx\), where p and q are constants. If f(1) = 7 and f(5) = 19, find f(3).

  • A 13
  • B 15
  • C 17
  • D 26
waec 2011furthermathematics

The correct answer is A. 13

\(f(x) = p + qx\)

\(f(1) = p + q(1) \implies p + q = 7 .... (1)\)

\(f(5) = p + 5q = 19 .....(2)\)

Solving for p and q using simultaneous equation, p = 4, q = 3

\(f(3) = 4 + 3(3) = 13\)

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