giải hộ mình vs ạ :)))))

`a)`

`A=(3x^2+5)·2x-x(3x-x^2)-x^2`

`A=6x^3+10x-3x^2+x^3-x^2`

`A=(6x^3+x^3)+(-3x^2-x^2)+10x`

`A=7x^3-4x^2+10x`

`b)`

`B=6(x^2-x)-x^2(4x-2)+4x(x^2-2x+3)`

`B=6x^2-6x-4x^3+2x^2+4x^3-8x^2+12x`

`B=(6x^2+2x^2-8x^2)+(-6x+12x)+(-4x^3+4x^3)`

`B=6x`

`c)`

`C=8x^3-5-(2x+1)(4x^2-x+1)`

`C=8x^3-5-(8x^3-2x^2+2x+4x^2-x+1)`

`C=8x^3-5-(8x^3+2x^2+x+1)`

`C=8x^3-5-8x^3-2x^2-x-1`

`C=-2x^2-x-6`