David M. answered 08/03/18
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Dave "The Math Whiz"
The least common denominator, lcd, is used when dealing with fractions and because neither of these are fractions the answer for lcd would be 1. However, the least common multiple, lcm, is the "least number that is a common multiple of two or more numbers".
First, find the prime factors of each number (polynomial)
a2b: a X a X b
ab2: a X b X b
Now, use each prime factor the greatest number of times that appears in any factorization
a X a X b ---> a2 X b--->2 a's and 1 b
a X b X b ---> a X b2--->1 a and 2 b's
Therefore, the lcm is a2 X b2, or a2b2.