có 1 câu hỏi mong mn giúp đỡ, cảm ơn nhiều

Câu `1:`

`a,`

`A(x)=4x-1+3x^3+x-2x^3-3x^2`

`A(x)=(3x^3-2x^3)-3x^2+(4x-x)-1`

`A(x)=x^3-3x^2+3x-1`

`B(x)=-2x^3+7+3x^3+x-6x^3+x^2`

`B(x)=(-2x^3+3x^3-6x^3)+x^2+x+7`

`B(x)=-5x^3+x^2+x+7`

`b,`

`A(x)+B(x)=(x^3-3x^2+3x-1)+(-5x^3+x^2+x+7)`

`A(x)+B(x)=x^3-3x^2+3x-1-5x^3+x^2+x+7`

`A(x)+B(x)=(x^3-5x^3)+(-3x^2+x^2)+(3x+x)+(-1+7)`

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

`A(x)-B(x)=(x^3-3x^2+3x-1)-(-5x^3+x^2+x+7)`

`A(x)-B(x)=x^3-3x^2+3x-1+5x^3-x^2-x-7`

`A(x)-B(x)=(x^3+5x^3)+(-3x^2-x^2)+(3x-x)+(-1-7)`

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