Answer
$y^3-6y^2+13y-12$
Work Step by Step
Using the Distributive Property, the given expression, $
(y-3)(y^2-3y+4)
,$ is equivalent to
\begin{array}{l}\require{cancel}
y(y^2)+y(-3y)+y(4)-3(y^2)-3(-3y)-3(4)
\\\\=
y^3-3y^2+4y-3y^2+9y-12
\\\\=
y^3+(-3y^2-3y^2)+(4y+9y)-12
\\\\=
y^3-6y^2+13y-12
.\end{array}
