$1).$Given $g(x,y,z)=e^{3z}sin(-4x)cos(y),$

gradg$=<mtext></mtext><mi></mi>$

$2).$Given $f(x,y)=5x^2-3xy+8y^2,$

gradf$=$

Then gradf$(-4,2)=$

$3).$Given $f(x,y)=-4x-xy+5y^2,$ find the directional derivative at $(x,y)=(2,-3)$ in the direction corresponding to $=\frac{2}{3}.$ Round to $5$ decimal places as necessary.