The prime factorizations of the two numbers are:
72 = 2 x 2 x 2 x 3 x 3 (sorry; can't use exponents in phpbb textbased language). This can also be expressed as 8 x 9, to help visualization.
98 = 2 x 7 x 7. Alternate expression: 2 x 49.
The only common factor, then, that 72 and 98 have in common is 2. Too bad you're not looking for factors in common for 72 and 96....that would be wonderful!
