Đáp án: `C=-2`
Giải thích các bước giải:
`ĐKXĐ:x\ne+-1`
`C=({x^2+x+1}/{x^2+x}-{x^2-x+1}/{x^2-x}).{x^4+x^3-x^2-x}/{x+1}`
`=[{x^2+x+1}/{x(x+1)}-{x^2-x+1}/{x(x-1)}].{x^3(x+1)-x(x+1)}/{x+1}`
`=[{(x-1)(x^2+x+1)}/{x(x+1)(x-1)}-{(x+1)(x^2-x+1)}/{x(x+1)(x-1)}].{(x^3-x)(x+1)}/{x+1}`
`={(x-1)(x^2+x+1)-(x+1)(x^2-x+1)}/{x(x+1)(x-1)}.{x(x^2-1)(x+1)}/{x+1}`
`={x^3-1-(x^3+1)}/{x(x+1)(x-1)}.{x(x-1)(x+1)(x+1)}/{x+1}`
`={x^3-1-x^3-1}/{x(x+1)(x-1)}.{x(x-1)(x+1)(x+1)}/{x+1}`
`={-2}/{x(x+1)(x-1)}.{x(x-1)(x+1)(x+1)}/{x+1}`
`=-2`
Vậy với `x\ne+-1` thì `C=-2`
