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JAMB Mathematics 2006 Question 38

Question 38

Polynomials

Find the roots of x3 − 2x2 − 5x + 6 = 0.

  1. A.1, 2, −3
  2. B.−1, −2, 3
  3. C.−1, 2, −3
  4. D.1, −2, 3
Show the answer and explanation

Answer: D (1, −2, 3)

Explanation

x = 1 gives 1 − 2 − 5 + 6 = 0. Dividing leaves x2 − x − 6 = (x − 3)(x + 2), so the roots are 1, −2, 3.