Question

$factorise = 3a2b - 12a2 - 9b + 36$
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Answer 1

Question:

$3 a ^ { 2 } b - 12 a ^ { 2 } - 9 b + 36$

Answer:

$3 a ^ { 2 } b - 12 a ^ { 2 } - 9 b + 36 \\ \\ = 3a {}^{2} (b - 4) - 9(b - 4) \\ \\ = (b - 4)(3a {}^{2} - 9) \\ \\ = (b - 4)3(a {}^{2} - 3) \\ \\ = 3(b - 4)(a {}^{2} - 3) \\ \\ = 3(b - 4)(a - 3)(a + 3) \\ \\ (x {}^{2} - y {}^{2} = (x - y)(x + y)) \\ \\ hence. \: 3a {}^{2} b - 12a {}^{2} - 9b + 36 \\ = 3(b - 4)(a - 3)(a + 3)$

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