(5m+n)(n-5m)-25m(m-6)
(5m+n)(n-5m)-25m(m-6)=5mn-25m^2+n^2-5mn-25m^2+150m=-50m^2+n^2+150m
простите, 150m
(5mn-25m^2+n^2-5mn)-(25m^2-150m) 5mn-25m^2+n^2-5mn-25m^2+150m -50m^2+n^2=150m Вроде так.
+150m*