Applying Boundary Conditions at Infinity?

I'm trying to solve the differential equation A*p''(x)-p(x)/B=0 with the
boundary conditions that p(infinity)=0 and p(xn)=pn.

Maxima easily finds the general solution.

ode2(A*'diff(p,x,2)-p/B,p,x);

Is  A B  positive or negative?
p
                                    x                         x
                               ---------------         - ---------------
                               sqrt(A) sqrt(B)    sqrt(A) sqrt(B)
(%o1)         p = %k1 %e                + %k2 %e

Applying the boundary conditions does not give the expected result
bc2(%o1,x=inf,p=0,x=xn,p=pn);

Maxima treats infinity as just another variable.  Can I make maxima figure
out that for p(infinity)=0 %k1 must be 0?  Since I know the answer I can
just set %k1 to zero, but it does not seem like a satisfactory solution.

I couldn't find anything in the manual about it.

Any help would be appreciated.

Thanks,
Chris