Suppose the PDE
PDE: $\quad u_{tt} = 9 u_{xx} , \qquad -\infty < x < \infty , \quad t > 0$
Has the solution $u(x,t) = A e^{x + 3 t} + B e^{x-3 t}$ for some numbers $A$ and $B$.
Suppose we know that $u(0,0) = 6$ and $u_t(x,0) = 0$ for all $x$. Then
$A = {}$
$B = {}$

help (numbers)