Question

2mn + 4n 2 and 5m 2 - 7mn

answers at bottom
1) 9m2 + 9mn - 4n2
2) 5m2 - 14mn - 4n2
3) 5m2 - 5mn + 4n2
4) 5m2 + 5mn - 4n2

Answer 1

`(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)`