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JAMB Mathematics 1998 Question 16

Question 16

Polynomials

Express in partial fractions (11x + 2)/(6x2 − x − 1)

  1. A.1/(3x − 1) + 3/(2x + 1)
  2. B.3/(3x + 1) − 1/(2x − 1)
  3. C.3/(3x − 1) − 1/(2x + 1)
  4. D.1/(3x + 1) + 3/(2x − 1)
Show the answer and explanation

Answer: D (1/(3x + 1) + 3/(2x − 1))

Explanation

6x² − x − 1 = (3x + 1)(2x − 1). Write 11x + 2 = A(2x − 1) + B(3x + 1); x = ½ gives B = 3 and x = −⅓ gives A = 1.