11. Let the line $y=a x-4$ be symmetric to the line $y=8 x-b$ with respect to the line $y=x$. Then $a=$ $\qquad$ ,$b=$ $\qquad$
II. 11. $\frac{1}{8},-32$.
It is easy to know that the equation of the line symmetric to $y=a x-4$ with respect to $y=x$ is
$$
\begin{array}{l}
y=\frac{1}{a} x+\frac{4}{a} . \\
\text { Therefore, } \frac{1}{a}=8, \frac{4}{a}=-b \Rightarrow a=\frac{1}{8}, b=-32 .
\end{array}
$$