Question
Factorise:
$84-2 r-2 r^2$
$84-2 r-2 r^2$
✓
Answer
$84-2 r-2 r^2$
$=-2\left(r^2+r-42\right)$
$=-2\left(r^2+7 r-6 r-42\right)$
$=-2[r(r+7)-6(r+7)]$
$=-2(r-6)(r+7)=2(6-r)(r+7)$
$=-2\left(r^2+r-42\right)$
$=-2\left(r^2+7 r-6 r-42\right)$
$=-2[r(r+7)-6(r+7)]$
$=-2(r-6)(r+7)=2(6-r)(r+7)$
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