$($a$)$ Find dy$,$ and $($b$)$ evaluate dy for the given value of $x$ and $dx.$

$y=x\sqrt[\phantom{2}]{4-2x^2},x=0,dx=-0\mathrm{.}3$

$($a$)$

$($Type an exact answer, using radicals as needed.$)$

$($b$)$ At the given values, $dy=.$

$($Type an integer or a decimal.$)$