# How do you factor y=3x^3 - 9x^2 ?

$y = 3 {x}^{2} \left(x - 3\right)$
$y = 3 \times x \times x \times x - 3 \times 3 \times x \times x$
Separate the common terms, $3 \times x \times x = 3 {x}^{2}$ and write the remaining terms in brackets:
$\implies y = 3 {x}^{2} \left(x - 3\right)$