Consider the function

$z=x^3+y^3-3x-3y$

$(a)$ What $is{z}_x(the$ partial derivative $ofz$ with respect $tox)?$

$3y$

$3x$

$-3x+3$

$3x^2-3$

$3x^2+3y^2$

$3x-3$

$-3$