Answer:
see below
Step-by-step explanation:
19. (4x + 8x² - 8) + (x² + 7 - 4x)
= 4x + 8x² - 8 + x² + 7 - 4x
= 8x² + x² + 4x - 4x -8 + 7
= 9x² - 1
20. (7x² - 11 + 16x) + (5x - 3x² - 7)
= 7x² - 11 + 16x + 5x - 3x² - 7
= 4x² + 21x - 18
22. (4x² - 12x - 10) - (2x² + x - 3)
= 4x² - 12x - 10 - 2x² - x + 3
= 2x² - 13x - 7
23. (7x³ - 9x² - 14x) - (4x³ - 4 - x)
= 7x³ - 9x² - 14x - 4x³ + 4 + x
= 7x³ - 4x³ - 9x² - 14x + x + 4
= 3x³ - 9x² - 13x + 4
25. (9x² + 24x - 8) - (5x² + 3x + 10)
= 9x² + 24x - 8 - 5x² - 3x - 10
= 4x² + 21x - 18
26. (5x - 12x² + 9x³) - (5x³ + 6x - 3)
= 5x - 12x² + 9x³ - 5x³ - 6x + 3
= 4x³ - 12x² - x + 3
28. (2x² - 1 + 3x³) + (5 - 13x - 11x²)
= 2x² - 1 + 3x³ + 5 - 13x - 11x²
= 3x³ - 9x² - 13x + 4
30. (10x - x² + 8) + (5x² + 1 - 22x)
= 10x - x² + 8 + 5x² + 1 - 22x
= 4x² - 12x + 9
