Найти производные 2 порядка. u=xyln(y-z)

[latex]u=xy\ln(y-z)\\ u_x=y\ln(y-z)\\ u_y=x\ln(y-z)+\dfrac{xy}{y-z}\\ u_z=\dfrac{xy}{z-y}\\ u_{xx}=0\\ u_{xy}=u_{yx}=\ln(y-z)+\dfrac{y}{y-z}\\ u_{xz}=u_{zx}=\dfrac y{z-y}\\ u_{yy}=\dfrac{2x}{y-z}-\dfrac{xy}{(y-z)^2}\\ u_{yz}=u_{zy}=\dfrac{x}{z-y}+\dfrac{xy}{(y-z)^2)}\\ u_{zz}=-\dfrac{xy}{(z-y)^2}[/latex]