How to easily define the following expressions

In this system of equations, I want to solve uppercase a (n, k) and b (n, k), everything else is known, because k is zero, so it's not easy to use the matrix operation in matlab, how to define the expression can make the operation more convenient. For example, whether you can use handle and so on.

If so, why not the following calculations

a=@(n,k)(besselj(w,1)^2+n^2+k^2)
%b=a+1;
b=@(n,k)(a+1)

This is just a simple example, and my question is, if you find the simplest way to define an expression, to solve the above problem.