Answer
$8x^3-12x^2+6x-1$
Work Step by Step
Using $(a+b)^3=a^3+3a^2b+3ab^2+b^3$ (or the cube of a binomial), the given expression, $
(2x-1)^3
,$ is equivalent to
\begin{array}{l}\require{cancel}
(2x)^3+3(2x)^2(-1)+3(2x)(-1)^2+(-1)^3
\\\\=
8x^3+3(4x^2)(-1)+3(2x)(1)-1
\\\\=
8x^3-12x^2+6x-1
.\end{array}
