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