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2. Polynomials
medium
गुणनखंड कीजिए
$84-2 r-2 r^{2}$
Option A
Option B
Option C
Option D
Solution
In order to factorise $84-2 r-2 r^{2}$, we have to find two numbers $p$ and $1$ such that $p+q=-2$ and $pq =-168.$
$\therefore \quad 84-2 r-2 r^{2}=-2 r^{2}-2 r+84$
$=-2 r^{2}-14 r+12 r+84$
$=-2 r(r+7)+12(r+7)$
$=(r+7)(-2 r+12)$
$=-2(r+7)(r-6)=-2(r-6)(r+7)$
Standard 9
Mathematics