If we use synthetic division, we would just need to write 2x+1 as 2(x+1/2) and then simply divide our resultant quotient by 2:
-1/2 | 4 0 7 9
________-2 1-4_
______4 -2 8|5
4x3+7x+9 = (x+1/2)(4x2-2x+8) + 5/(x+1/2)
4x3+7x+9 = (2x+1)(2x2-x+4) + 10
Hope this helped!