# How do you factor 3x^2 -9x=0 ?

$3 {x}^{2} - 9 x = 3 x \left(x - 3\right)$
Check first for a common factor. In this case it is $3 x$.
Divide each term by $3 x$ and write the 'left-over' from each term in the bracket.
$3 {x}^{2} - 9 x = 3 x \left(x - 3\right)$