# How do you simplify sqrt(486y^2)?

$\sqrt{486 {y}^{2}} = \sqrt{6 \cdot 81 \cdot {y}^{2}} = \sqrt{6 \cdot {\left(9 y\right)}^{2}} = 9 \sqrt{6} \cdot | y |$
The $| y |$ is necessary to cover the case $y < 0$.