\[\frac{x^{2} - 7x}{\sqrt{x - 6} + 1} =\]
\[= \frac{x(x - 7)\left( \sqrt{x - 6} - 1 \right)}{\left( \sqrt{x - 6} + 1 \right)\left( \sqrt{x - 6} - 1 \right)} =\]
\[= \frac{x(x - 7)\left( \sqrt{x - 6} - 1 \right)}{x - 6 - 1} =\]
\[= x \cdot (\sqrt{x - 6} - 1)\]