SOLUTION: Find the LCM of (9+7r), (81-49r^2), and (9-7r) Thanks, Dee

Question 515185: Find the LCM of (9+7r), (81-49r^2), and (9-7r)
Thanks,
Dee

Answer by drcole(72) (Show Source): You can put this solution on YOUR website!
To find the least common multiple, we need to first factor each of the expressions. The first, , and the third, , cannot be factored, but the second, , is the difference of two squares:
and
Remembering that every difference of two squares can be factored as:

we get that

So we are trying to find the least common multiple of , , and . The least common multiple of three expressions A, B, and C is the simplest expression that contains A, B, and C in its factorization. So the least common multiple has to contain at least one and one in its factorization, since those appear in A and C. Do we need anything else? No, because , so doesn't add any new factors to the least common multiple. So the least common multiple must be or .
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