Common factor of 2a2b, 4ab2, 6ac2 :

If a number is the factor of two or more numbers, then that number is called a common factor of those numbers.

Determine the common factor:

2a2b = 1 × 2 × 2 × a × b

4ab2 = 1 × 2 × 2 × 2 × a × b

6ac2 = 1 × 2 × 2 × 3 × a × c

Common factor = 2 × 2 × a = 4a