Factor the expression m^2-3mn-28n^2

(m-7n) (m+4n)

Since a is equal to 1, the equation can be factored by finding factors that multiply to c and adds to b and add each of the factor to m.

find factor that multiplies to - 28n^2 and adds to - 3n

-7n times 4n is - 28n^2 and - 7n plus 4n is - 3n