Answer
$5(2x-1)(x-3)$
Work Step by Step
For the polynomial
$$
10x^2 -35x +15=5(2x^2 -7x +3)
$$
we check the factors of $ac=2(3)=6$. The only factors that can give the right middle term are $-6$ and $-1$, as follows
$$
10x^2 -35x +15=5(2x^2 -7x +3)=5(2x-1)(x-3)
.$$
