How do you factor m^2 - mv- 56v^2?

${m}^{2} - m v - 56 v 2 = \left(m + 7 v\right) \left(m - 8 v\right)$.
Problem: Factor ${m}^{2} - m v - 56 {v}^{2}$.
Find two numbers that when added equal $- 1$ and when multiplied equal $- 56$.
The numbers $7$ and $- 8$ fit the criteria.
The factors of ${m}^{2} - m v - 56 {v}^{2}$ are $\left(m + 7 v\right) \left(m - 8 v\right)$.