Solve the following problems
a) $
\begin{array}{c}
\frac{\partial u}{\partial t}+3 x \frac{\partial u}{\partial x}=1+u, \quad- \infty0 \\
u(x, 0)=f(x)
\end{array}
$ b) $
\begin{array}{c}
t \frac{\partial u}{\partial t}+2 x \frac{\partial u}{\partial x}=1, \quad-
\infty1 \\
u(x, 1)=f(x)
\end{array}
$
SP. JG. 106