Question: polynomial inequalities/semidefiniteness

Hi,
not being used to work with Maple, I cannot figure out how to solve the following problem.

I want to verify if the positive semidefiniteness of a given 20x20 matrix A (depending on 10 real variables x_1, ..., x_10) implies the positive semidefiniteness of another 4x4 matrix B (depending on the same 10 variables). The entries of each matrix are linear in the given variables, at most depending on 3 variables. The 20x20 matrix is rather sparse.

What I tried is the following:

assume(x_1, real, ..., x_10, real):
constA:={op(convert(IsDefinite(A, query=positive_semidefinite), boolean_function))}:
for i from 1 to ... by 1 do additionally(constA[i]) end do;

IsDefinite(B, query=positive_semidefinite);

The result was that the calculation went on for over half an hour without giving a result. Is that normal?

I also tried to check seperately each constraint for the semidefiniteness of B:
constB:={op(convert(IsDefinite(B, query=positive_semidefinite), boolean_function))}:
 

for i from 1 to ... by 1 do is(constB[i]) end do;

As above, I did not get any results. Am I making a mistake? Maybe someone can help me out. Thanks!