z=f(x,y)=x^3 + x^2 * y + x^2 ln(2+y)+e^(x+5) *y
dz/dx=3x^2+2xy+2xln(2+y)+e^(x+5)*y =3x^2+2x[y+ln(2+y)]+e^(x+5)*y
dz/dy=x^2 +x^2 /(2+y)+e^(x+5)