How do I divide polynomials. My issue is generally that I don't understand where to put negative numbers for the second bit.

. Divide x - 2 into x4 - 11x3 + 21x2 + x - 10 .

The answer is

x4 - 11x3 + 21x2 + x - 10 = (x3 - 9x2 + 3x + 7)(x - 2) + 4

But, how do I get there? Could you please explain it? Thanks.