Question 1188645

the difference of {{{(7m^2n-2mn^2) }}}and {{{(-m^2n+9mn^2)}}} is

{{{(7m^2n-2mn^2) - (-m^2n+9mn^2)=7m^2n-2mn^2+m^2*n-9mn^2=8m^2n - 11mn^2}}}

add ({{{5m^2n+3mn-6mn^2}}}) to it

{{{8m^2n - 11mn^2+5m^2n+3mn-6mn^2}}}

={{{13m^2n - 17mn^2 + 3mn}}}

so, {{{(7m^2n-2mn^2) - (-m^2n+9mn^2)+(5m^2n+3mn-6mn^2) =13m^2n - 17mn^2 + 3mn}}}