Simplify and write your final answer in factored form.
(9r3+2r2-5r+4)-(5r3-7r+4)
= 9r^3 + 2r^2 - 5r + 4 - 5r^3 + 7r - 4
= (9r^3 - 5r^3) + 2r^2 - 5r + 7r + (4 - 4)
= 4r^3 + 2r^2 + 2r
= 2r(2r^2 + r + 1)
(9r3+2r2-5r+4)-(5r3-7r+4)
= (9r^3 - 5r^3) + 2r^2 - 5r + 7r + (4 - 4)
= 4r^3 + 2r^2 + 2r
= 2r(2r^2 + r + 1)