The factorization below is missing two positive integers a and b.

$\displaystyle{5}{{x}}^{{4}}+{40}{{x}}^{{3}}-{100}{{x}}^{{2}}={5}{{x}}^{{2}}{\left({x}-{a}\right)}{\left({x}+{b}\right)}\usepackage{cmbright}\Huge\$

Factor the polynomial and then supply the value of a.

(Do not include the minus sign.)