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JAMB Mathematics 2021 past questions and answers

1 questions. Try each one, then open the answer to check yourself and read the explanation.

Question 24

Algebraic Expressions

Factorize completely 4a² − 12ab − c² + 9b².

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

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

Explanation

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

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