Cho hàm số \[z = f(x,y) = {x^{20}} + {y^{20}} + {x^{10}}{y^{11}}\]. Chọn đáp án đúng?

\[z_{{x^{_3}}{y^{_{19}}}}^{22} = z_{{y^{_3}}{x^{_{19}}}}^{22} = 1\]

\[z_{{x^{_{13}}}{y^{_{19}}}}^{22} = z_{{y^6}{x^{_{16}}}}^{22} = 2\]

\[z_{{x^7}{y^{_{15}}}}^{22} = z_{{y^6}{x^{_{16}}}}^{22} = 0\]

\[z_{{x^{_{11}}}{y^{_{11}}}}^{22} = z_{{y^{11}}{x^{_{11}}}}^{22} = 3\]