Answer
$x^3-125$
Work Step by Step
Using $a(b+c)=ab+ac$ or the Distributive Property, the given expression, $
(x-5)(x^2+5x+25)
$, is equivalent to
\begin{array}{l}\require{cancel}
x(x^2)+x(5x)+x(25)-5(x^2)-5(5x)-5(25)
\\\\=
x^3+5x^2+25x-5x^2-25x-125
\\\\=
x^3+(5x^2-5x^2)+(25x-25x)-125
\\\\=
x^3+0x^2+0x-125
\\\\=
x^3-125
.\end{array}
