1. -2a+3b-8a+7b 2. 3x²-5xy+7xy-10x²+y² 3. 2x²y-3ab³-4x²y-5ab³ 4. 2a²-3ab-3a²+7ab-4b² 5. -3c+2d-4c-5d 6. 3a³b-4xy²-5xy²+7a³b

1. -2a + 3b - 8a + 7b = (-2a - 8a) + (3b + 7b) = -10a + 10b

2. 3x² - 5xy + 7xy - 10x² + y² = (3x² - 10x²) + (-5xy + 7xy) + y² = -7x² + 2xy + y²

3. 2x²y - 3ab³ - 4x²y - 5ab³ = (2x²y - 4x²y) + (-3ab³ - 5ab³) = -2x²y - 8ab³

4. 2a² - 3ab - 3a² + 7ab - 4b² = (2a² - 3a²) + (-3ab + 7ab) - 4b² = -a² + 4ab - 4b²

5. -3c + 2d - 4c - 5d = (-3c - 4c) + (2d - 5d) = -7c - 3d

6. 3a³b - 4xy² - 5xy² + 7a³b = (3a³b + 7a³b) + (-4xy² - 5xy²) = 10a³b - 9xy²

Ответ: 1) -10a+10b; 2) -7x²+2xy+y²; 3) -2x²y-8ab³; 4) -a²+4ab-4b²; 5) -7c-3d; 6) 10a³b-9xy²