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WAEC Mathematics 2005 Question 32

Question 32

Graphs of Functions

The figure is the graph of a quadratic equation. What is the equation of the curve?

Diagram for this question
  1. A.y = x2 + 6x + 4
  2. B.y = x2 − 5x − 4
  3. C.y = x2 − 5x + 4
  4. D.y = x2 + 5x − 4
Show the answer and explanation

Answer: C (y = x2 − 5x + 4)

Explanation

Roots 1 and 4 give y = (x − 1)(x − 4) = x2 − 5x + 4 (it also passes through (0, 4)).