Đáp án + Giải thích các bước giải:
`A=x^4+2x^3-16x^2-2x+15`
`=>A=x^4+x^3+x^3+x^2-17x^2-17x+15x+15`
`=>A=x^3(x+1)+x^2(x+1)-17x(x+1)+15(x+1)`
`=>A=(x+1)(x^3+x^2-17x+15)`
`=>A=(x+1)(x^3-x^2+2x^2-2x-15x+15)`
`=>A=(x+1)[x^2(x-1)+2x(x-1)-15(x-1)]`
`=>A=(x+1)(x-1)(x^2+2x-15)`
`=>A=(x+1)(x-1)(x^2+5x-3x-15)`
`=>A=(x+1)(x-1)[x(x+5)-3(x+5)]`
`=>A=(x+1)(x-1)(x+5)(x-3)`
Vì `x` lẻ
`=>` $\left\{\begin{matrix}
x+1\ chẵn\\x-1\ chẵn\\x+5\ chẵn\\x-3\ chẵn \end{matrix}\right.$
`=>(x+1)(x-1)(x+5)(x-3)\ chẵn`
Vậy `A\ chẵn`
