Answer
$x^4+x^3-6x^2-5x+5$
Work Step by Step
Using $a(b+c)=ab+ac$ or the Distributive Property, the given expression, $
(x^2-5)(x^2+x-1)
$, is equivalent to
\begin{array}{l}\require{cancel}
x^2(x^2)+x^2(x)+x^2(-1)-5(x^2)-5(x)-5(-1)
\\\\=
x^4+x^3-x^2-5x^2-5x+5
\\\\=
x^4+x^3+(-x^2-5x^2)-5x+5
\\\\=
x^4+x^3-6x^2-5x+5
.\end{array}
