Answer:
[tex]\dashrightarrow \: { \tt{( {5xy}^{2} + 3 {x}^{2} - 7) + (3 {x}^{2} {y}^{2} - x {y}^{2} - 3 {y}^{2} + 4) }} \\ \\\dashrightarrow \: { \tt{3 {x}^{2} {y}^{2} - 3 {y}^{2} + 3 {x}^{2} + (5 - 1) {xy}^{2} + (4 - 7) }} \\ \\ \dashrightarrow \: { \boxed{ \tt{ {3x} {y}(xy + x - y - 1) + 4 {xy}^{2} }}}[/tex]
