\[\frac{a}{b} = 10 \Longrightarrow \frac{b}{a} = \frac{1}{10} = 0,1 \Longrightarrow a =\]
\[= 10b\]
\[\frac{(a - b)^{2}}{\text{ab}} = \frac{(10b - b)^{2}}{10b^{2}} =\]
\[= \frac{(9b)^{2}}{10b^{2}} = \frac{81b^{2}}{10b^{2}} = 8,1\]