solving unknowns in matrix - in Maxima

Greetings --

Consider the following matrix:

a : matrix([-0.7-0.3*h1,0.6-0.6*h1],[0.5-0.5*h2,-0.35-0.65*h2]);

I'm trying to solve for h1 and h2, such that dominant eigenvalue of a is 0.

I know how to do this in a couple of other CAS systems, but am stumped 
with Maxima. I know the solution in thiscase is

h2=(11-81*h1)/(151-21*h1)

Any pointers would be much appreciated (to aid and abet my attempt to 
port a bunch of teaching material to Maxima).

Thanks!