Hàm số

B

- Hướng dẫn giải

Đáp án B

$f\left(x\right)=\frac{x^2+x+1}{x+1}$ TXD $D=R\backslash \left\{-1\right\}$

$\begin{array}{l}f\text{'}\left(x\right)=\frac{\left(2x+1\right)\left(x+1\right)-x^2-x-1}{{\left(x+1\right)}^2}=\frac{x^2+2x}{{\left(x+1\right)}^2}\\ f\text{'}\left(x\right)=0\iff x^2+2x=0\iff \left[\begin{array}{l}x=0\\ x=-2\end{array}\right.\end{array}$