How subtracting polynomials differs from adding polynomials and examples?

All you need to do is distribute the subtraction sign to all of the numbers in the polynomial being subtracted. Ex: (6x^4+8x^3-3)-(2x^2-9x+9)  you distribute the subtraction sign in the (2x^2-9x+9) and get -2x^2+9x-9. Next, all you have to do is combine like terms. 6x^4+8x^3-3-2x^2+9x-9 Turns into 6x^4+8x^3-2x^2+9x-12