Question

Factorise x^2 -y^2 - 8y -16

Answer 1

$x {}^{2} - y {}^{2} - 8y - 16 \\ = x {}^{2} - (y {}^{2} + 8y + 16) \\ = x {}^{2} - ( \: (y) {}^{2} + 2 \times y \times 4 + (4) {}^{2} ) \\ = x {}^{2} - (y + 4) {}^{2} \\ = (x + y + 4)(x - y - 4)$


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