a^2 + ab - 56b^2
Factor by grouping is typically done when you have 4 terms not 3.
This is a trinomial that is factorable as is.
If it has to be done by grouping I can do that also. Let me know.
What are the factors of -56 that add up to 1?
8 * (-7) = -56
8 + (-7) = 1
(a + 8b)(a - 7b)
