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UI Post-UTME Mathematics 2018 (Model questions) Question 38

Question 38

Quadratic Equations

A boy thinks of a number. He squares it and subtracts from it the original number, the result is 42. What is the number?

  1. A.6 or 8
  2. B.7 or −6
  3. C.9 or 6
  4. D.7 or 8
Show the answer and explanation

Answer: B (7 or −6)

Explanation

x² − x − 42 = 0, (x − 7)(x + 6) = 0, so x = 7 or −6.