The Greatest Common Factor (GCF) for 120 and 72, notation CGF(120,72), is 24. Explanation: The factors of 120 are 1,2,3,4,5,6,8,10,12,15,20,24,30,40,60,120; The factors of 72 are 1,2,3,4,6,8,9,12,18,24,36,72.
Look at each coefficient next to the degree of the radical. When inputting that number for synthetic division (From greatest degree to least) you would get 8 1 and -5. The number that is the divisor is the 6, but you have to set (x - 6) to equal zero, which would get you a number of 6.