2m + 1
—————— × (9m² - 36)
3m - 6
Write the second part over 1
2m + 1 9m² - 36
—————— × ————————
3m - 6 1
Factor 3m - 6 as 3(m - 2)
Factor 9m² - 36 first as 9(m² - 4) and then as
9(m - 2)(m + 2).
2m + 1 9(m - 2)(m + 2)
———————— × ———————————————
3(m - 2) 1
Cancel the 3 factor of the bottom first fraction
into the 9 factor in the top of the second fraction:
3
2m + 1 9(m - 2)(m + 2)
———————— × ———————————————
3(m - 2) 1
1
Now cancel the (m - 2) factor of the bottom first
fraction into the (m - 2) factor in the top of the
second fraction:
3 1
2m + 1 9(m - 2)(m + 2)
———————— × ———————————————
3(m - 2) 1
1 1
2m + 1 3(m + 2)
———————— × ————————
1 1
Put parentheses around the 2m + 1 as (2m + 1)
(2m + 1) 3(m + 2)
———————— × ————————
1 1
Indicate multiplication of numerators
(2m + 1)3(m + 2)
————————————————
1
Erase the 1 denominator and just write the numerator
(2m + 1)3(m + 2)
It is preferable to put the shorter factors first:
3(m + 2)(2m + 1)
That is an acceptable answer. If you like you can
"FOIL" out the two parenthetical binomials:
3(2m² + m + 4m + 2)
then combine the m with the 4m getting 5m
3(2m² + 5m + 2)
then distribute the 3
6m² + 15m + 6
However leaving it in the factored form above
is just as good.
Edwin
AnlytcPhil@aol.com