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JAMB Mathematics 1989 Question 21

Question 21

Algebraic Expressions

Factorize 4a2 − 12ab − c2 + 9b2

  1. A.4a(a − 3b) + (3b − c)2
  2. B.(2a + 3b − c)(2a + 3b + c)
  3. C.(2a − 3b − c)(2a − 3b + c)
  4. D.4a(a − 3b) + (3b + c)2.
Show the answer and explanation

Answer: C ((2a − 3b − c)(2a − 3b + c))

Explanation

4a² − 12ab + 9b² = (2a − 3b)², so the expression is (2a − 3b)² − c² = (2a − 3b − c)(2a − 3b + c).