Đáp án + Giải thích các bước giải:
a)
`P(x)=x^2+5x^4-3x^3+x^2+4x^4+3x^3-x+5`
`<=>P(x)=(x^2+x^2)+(5x^4+4x^4)-(3x^3-3x^3)-x+5`
`<=>P(x)=2x^2+9x^4-x+5`
Sắp xếp: `P(x)=9x^4+2x^2-x+5`
`Q(x)=x-5x^3-x^2-x^4+4x^3-x^2+3x-1`
`<=>Q(x)=(x+3x)-(5x^3-4x^3)-(x^2+x^2)-x^4-1`
`<=>Q(x)=4x-x^3-2x^2-x^4-1`
Sắp xếp: `Q(x)=-x^4-x^3-2x^2+4x-1`
b)
`P(x)+Q(x)=9x^4+2x^2-x+5-x^4-x^3-2x^2+4x-1`
`<=>(9x^4-x^4)+(2x^2-2x^2)-(x-4x)+(5-1)-x^3`
`<=>8x^4+3x+4-x^3`
`P(x)-Q(x)=(9x^4+2x^2-x+5)-(-x^4-x^3-2x^2+4x-1)`
`<=>9x^4+2x^2-x+5+x^4+x^3+2x^2-4x+1`
`<=>(9x^4+x^4)+(2x^2+2x^2)-(x+4x)+(5+1)+x^3`
`<=>10x^4+4x^2-5x+6+x^3`