-----------------------------------
x+9 | x^3 + 10x^2 + 13x + 36
x^2
-----------------------------------
x+9 | x^3 + 10x^2 + 13x + 36
- x^3 + 9 x^2
x^2 + 13x + 36
x^2 + x
-----------------------------------
x+9 | x^3 + 10x^2 + 13x + 36
- x^3 + 9 x^2
x^2 + 13x + 36
- x^2 + 9x
4x + 36
x^2 + x + 4
-----------------------------------
x+9 | x^3 + 10x^2 + 13x + 36
- x^3 + 9 x^2
x^2 + 13x + 36
- x^2 + 9x
4x + 36
- 4x + 36
0
(x^3 + 10x^2 + 13x + 36) / (x+9) = x^2 + x + 4
I hope this makes sense lol