Algebra 1

$7(3z-7)(z-1)$
Factor each expression. $21z^{2}-70z+49$ Factor out a $7$ $7(3z^{2}-10z+7) Rewrite as:$7(3z^{2}-3z-7z+7) Factor: $7(3z(z-1)-7(z-1))$ Factor: $7(3z-7)(z-1)$