Bài 2:
a) `x(2x^2 - 3) - x^2(5x + 1) + x^2`
`= 2x^3 - 3x - 5x^3 - x^2 + x^2`
`= (2x^3 - 5x^3) - (x^2 - x^2) - 3x`
`= -3x^3 - 3x`
b) `3x(x - 2) - 5x(1 - x) - 8(x^2 - 3)`
`= 3x^2 - 6x - 5x + 5x^2 - 8x^2 + 24`
`= (3x^2 + 5x^2 - 8x^2) - (6x + 5x) + 24`
`= 11x + 24`
c) `1/2x^2(6x - 3) - x(x^2 + 1/2) + 1/2(x + 4)`
`= 3x^3 - 3/2x^2 - x^3 - 1/2x + 1/2x + 2`
`= (3x^3 - x^3) - 3/2x^2 - (1/2x - 1/2x) + 2`
`= 2x^3 - 3/2x^2 + 2`
Quy tắc nhân đơn thức với đa thức:
`A.(B + C) = A.B + A.C`