[m]=\frac{2y^2}{3}\cdot (-\frac{1}{2}) \cdot x^{-\frac{3}{2}} +6y\cdot 2x=[/m]
[m]=-\frac{y^2}{3\sqrt{x^{3}}} +12xy[/m]
[m]z`_{y}=\frac{2}{3\sqrt{x}}\cdot(y^2)`+6x^2\cdot y`=\frac{2}{3\sqrt{x}}\cdot(2y)+6x^2\cdot 1=\frac{4y}{3\sqrt{x}}+6x^2[/m]
[m]z`_(x)+z`_(y)=-\frac{y^2}{3\sqrt{x^{3}}} +12xy + \frac{4y}{3\sqrt{x}}+6x^2[/m]
[m](z`_(x)+z`_(y))|_{M}=-\frac{1^2}{3\sqrt{1^{3}}} +12\cdot 1\cdot 1 + \frac{4\cdot 1}{3\sqrt{1}}+6\cdot 1^2=19[/m]