1. x²-3xy+5+2x²+5xy 2. 5y-3x+6-8y+6x 3. ab+3a-5ab+7-6a+3

1. x² - 3xy + 5 + 2x² + 5xy = (x²+2x²) + (-3xy+5xy) + 5 = 3x² + 2xy + 5
2. 5y - 3x + 6 - 8y + 6x = (-3x+6x) + (5y-8y) + 6 = 3x - 3y + 6
3. ab + 3a - 5ab + 7 - 6a + 3 = (ab-5ab) + (3a-6a) + (7+3) = -4ab - 3a + 10.
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