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JAMB Mathematics 1986 Question 17

Question 17

Algebraic Expressions

Factorize completely 8a + 125ax3

  1. A.(2a + 5x2)(4 + 25ax)
  2. B.a(2 + 5x)(4 − 10x + 25x2)
  3. C.(2a + 5x)(4 − 10ax + 25x2)
  4. D.a(2 + 5x)(4 + 10ax + 25x2).
Show the answer and explanation

Answer: B (a(2 + 5x)(4 − 10x + 25x2))

Explanation

Take out a: a(8 + 125x³) = a(2³ + (5x)³). A sum of cubes factorises as (2 + 5x)(4 − 10x + 25x²).