Question
Factorise: $28-31 x-5 x^2$
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Answer
$28-31 x-5 x^2$
$=28-35 x+4 x-5 x^2$
${28 × (-5) = -140, -140 = -35 × 4, -31 = -35 + 4}$
$= 7(4 - 5x) + x(4 - 5x)$
$= (4 - 5x)(7 + x)$
$=28-35 x+4 x-5 x^2$
${28 × (-5) = -140, -140 = -35 × 4, -31 = -35 + 4}$
$= 7(4 - 5x) + x(4 - 5x)$
$= (4 - 5x)(7 + x)$
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