Respuesta :

gmany

[tex](2mn+4n^2)+(5m^2-7mn)\\\\=2mn+4n^2+5m^2-7mn\qquad\text{combine like terms}\\\\=5m^2+(2mn-7mn)+4n^2\\\\=\boxed{5m^2-5mn+4n^2}\to 3)[/tex]