The highest common factor of 12ab and 18a^2 is 6a
This is because 6a*2b=12ab and 6a*3a= 18a^2, and 2b and 3a have no common factors at all.
you find this out by making a prime number factor tree. 12ab prime numbers (this includes variables) are 3*2*2*a*b= 12ab and 3*3*2*a*a are the prime numbers (and variables) for 18a^2
the common prime factors are 3,2, and a, which you multiply together, then it equals 6a.
This is because 6a*2b=12ab and 6a*3a= 18a^2, and 2b and 3a have no common factors at all.
you find this out by making a prime number factor tree. 12ab prime numbers (this includes variables) are 3*2*2*a*b= 12ab and 3*3*2*a*a are the prime numbers (and variables) for 18a^2
the common prime factors are 3,2, and a, which you multiply together, then it equals 6a.