I didn't find a general expression. You notice that for the term independent of 'x', the 'x' terms of each bracket must cancel out. Now consider the powers of 'x' in each bracket:
The first bracket can have powers:
x^0, x^1, x^2
The second bracket can have powers:
x^5, x^3, x^1, x^-1, x^-3, x^-5
Now we just match them up so that the 'x' from each bracket cancel out, that is, when we take a power from the first bracket and add a power from the second bracket, we want it to equal 0. This only occurs when the first bracket is x^1 and the second bracket is x^-1. Thus finding the co-efficient at these powers:
First bracket: 3^1 x (-2)^1
Second bracket: 5C3 x 1^2 x 2^3
Multiply the two brackets together gives:
3^1 x (-2)^1 x 5C3 x 1^2 x 2^3 = -960