TeX Quellcode:
\begin{array}{rcl}f'_{yy}(x,y) &=& \dfrac{0\cdot\left(x+9y\right)^2-\left(-54\ln(x)\cdot 2\left(x+9y\right)^{2-1}\cdot 9\right)}{\left(x+9y\right)^4} \\\\&=& \dfrac{54\ln(x)\cdot 18\left(x+9y\right)}{\left(x+9y\right)^4} \\\\&=& \dfrac{972\ln(x)}{\left(x+9y\right)^3}\end{array}