Answer
$-7y(y-1)(y-2)$
Work Step by Step
$-7y^{3}+21y^{2}-14y\qquad$...factor out the common term, $-7y$
$=-7y(y^{2}-3y+2)$
Two factors of $ac=2$, whose sum is $b=-3$
are $-1$ and $-2$.
Rewrite the middle term and factor in pairs.
$-7y(y^{2}-3y+2)$
$=-7y(y^{2}-y-2y+2)$
$=-7y[y(y-1)-2(y-1)]\qquad$...factor out the common binomial factor,$y-1$.
$=-7y(y-1)(y-2)$
