converting a symbolic vector into a matrix vector product.

my problem is the following:

[b1;b2]=[a11,a12;a21,a22]*[p1;p2]

how do i find the matrix A so that this equation is statisfied.

(in my specific case b1=0 and b2 is a long expession involving terms with both p1 and p2)

[Dyuman Joshi]

Have you tried using solve?

Also, provide the expression for b2 and values for variables, if any.

[John D'Errico]

If b1, b2, p1, p2 are the only givens, then you cannot do so. Actually, you could, but there are infinitely many possible solutions. This is an underdetermined problem. So you cannot solve the problem in a unique way.

But worse, I see also the comment that b2 involves terms that have both p1 and p2 inside. That means you effectively have a system of apparently nonlinear equations, but only 2 equations, and 4 unknowns that you wish to solve for, thus rhe elements of A. Now you have an underdetermined nonlinear problem. so still no unique soluitons.