Question 148060
Find the factors for the quadratic terms and then cancel to simplify.
{{{2m^2-5mn-12n^2}}} = {{{(2m+3n)(m-4n)}}}
{{{2m^2-7mn-4n^2}}} = {{{(2m +1n)(m-4n)}}}
{{{m^2-8mn+16n^2}}} = {{{(m-4n)(m-4n)}}}

Now cancel what you can, remembering that dividing by a fraction is just the same as multiplying by that fractions inverse.

Ping if you cant get it