Đáp án:
`a, (5x - 2y)(x^2 - xy + 1) = 5x^3 - 5x^2.y + 5x - 2x^2.y + 2xy^2 - 2y`
`= 5x^3 + (- 5x^2.y - 2.x^2.y) + 2xy^2 + 5x - 2y`
`= 5x^3 - 7x^2.y + 2xy^2 + 5x - 2y`
`c, 1/2 x^2.y^2(2x + y)(2x - y)`
`= (x^3.y^2 + 1/2.x^2.y^3)(2x - y)`
`= 2x^4.y^2 + 1/2.x^2.y^4`
`e, (x - 7)(x - 5) = x^2 - 5x - 7x + 35`
`= x^2 + (-5x - 7x) + 35`
`= x^2 - 12x + 35`
`h, (2b^2 - 2 - 5b + 6b^3)(3 + 3b^2 - b)`
`= 6b^2 + 6b^4 - 2b^3 - 6 - 6b^2 + 2b - 15b - 15b^3 + 5b^2 + 18b^3 + 18b^5 - 6b^4`
`= (6b^2 - 6b^2) + (6b^4 - 6b^4) + (- 2b^3 - 15b^3 + 18b^3) + (2b - 15b) + 18b^5 - 6`
`= b^3 - 13b + 18b^5 - 6`
`= 18b^5 + b^3 - 13b - 6`
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