Step 1 :\(\frac{9x^3}{3x} = 3x^2\)
Step 2 :\((9x^3 + 6x^2) - (3x^2(3x+1)) = 3x^2 + 28x + 9\)
Step 3 :\(\frac{3x^2}{3x} = x\)
Step 4 :\((3x^2 + 28x + 9) - (x(3x+1)) = 27x + 9\)
Step 5 :\(\frac{27x}{3x} = 9\)
Step 6 :\((27x + 9) - (9(3x+1)) = 0\)
Step 7 :\(\boxed{3x^2 + x + 9}\)