Đáp án :
`M=-1`
Giải thích các bước giải :
`M=x^5-2021x^4+2021x^3-2021x^2+2021x-2021`
`=>M=(x^5-2020x^4)-(x^4-2020x^3)+(x^3-2020x^2)-(x^2-2020x)+(x-2020)-1`
`=>M=x^4(x-2020)-x^3(x-2020)+x^2(x-2020)-x(x-2020)+(x-2020)-1`
`=>M=x^4(2020-2020)-x^3(2020-2020)+x^2(2020-2020)-x(2020-2020)+(2020-2020)-1`
`=>M=x^(4).0-x^(3).0+x^(2).0-x.0+0-1`
`=>M=0-0+0-0+0-1`
`=>M=-1`
Vậy : `M=-1`