$\text{Bài 1:}$
`a, 3x(4x^2 - 2/3 x) = 12x^2 - 2x`
`b, 2x^3(5x^2 + 3x - 1) = 10x^5 + 6x^4 - 2x^3`
`c, -5x^2(-3x^2 + 4x - 2) = 12x^4 - 20x^3 + 10x^2`
`d, 2xy^2(3x^2y - 4x) = 6x^3y^3 - 8x^2y^2`
`e, -2xy(xy^2 - 2x^2y + 3) = -2x^2y^3 + 4x^3y^2 - 6xy`
`f, (-3x^3y + 5x^2y^4 - 1) . 2xy^3 = -6x^4y^4 + 10x^3y^7 - 2xy^3`
$\text{Bài 2:}$
`a, 5x(2x - 1) - 2x(5x + 4) = 10`
`⇔ 10x^2 - 5x - 10x^2 - 8x = 10`
`⇔ -13x = 10`
`⇔ x = -10/13`
`b, 4x(3 - 6x) + 3x(8x - 2) + 2x - 1 = 0`
`⇔ 12x - 24x^2 + 24x^2 - 6x + 2x - 1 = 0`
`⇔ 8x = 1`
`⇔ x = 1/8`
