Question 234514
Remove the common factor found in each term.

Then divide each term by that common factor.

The common factor found in each term is 3.

Do you see 3 in each term?

3m^2 divide by 3 = m^2

3n^2 divide by 3 = n^2

We now have this: 3(m^2 - n^2)

Inside the parentheses, we have what is called the difference of two perfect squares.  We can factor that out to be (m - n)(m + n).

Final answer: 3(m - n)(m + n)

NOTICE:  The final answer has 3 factors.  Do you see the factors?