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JAMB Mathematics 1988 Question 25

Question 25

Graphs of Functions

Use the graph of y = (x2 + 3)/(x + 4) and y = 1 to answer this question. What is the solution of the equation x2 − x − 1 = 0?

Diagram for this question
  1. A.x = 1.6 and x = −0.6
  2. B.x = −1.6 and x = 0.6
  3. C.x = 1.6 and x = 0.6
  4. D.x = −1.6 and x = −0.6.
Show the answer and explanation

Answer: A (x = 1.6 and x = −0.6)

Explanation

Setting (x² + 3)/(x + 4) = 1 gives x² + 3 = x + 4, i.e. x² − x − 1 = 0. So the roots are where the curve meets the line y = 1, at about x = 1.6 and x = −0.6.