Answer:
[tex]7x^{3} + 8x^{2} -8x + 7[/tex]
Step-by-step explanation:
[tex](8x^{2} - 5x + 7) + (7x^{3} - 3x) = 8x^{2} - 5x + 7 + 7x^{3} - 3x = 7x^{3} + 8x^{2} - 5x - 3x + 7 = 7x^{3} + 8x^{2} -8x + 7[/tex]
7x³ + 8x² -8x + 7
8x² - 5x +7 + 7x³ - 3x
7x³ + 8x² + (-5x -3x ) + 7
