Hàm số

D

- Hướng dẫn giải

Đáp án D

Ta có $y\text{'}=\frac{x\text{'}.(x-2)-x.(x-2)\text{'}}{{(x-2)}^2}=\frac{1.(x-2)-x.1}{{(x-2)}^2}=\frac{-2}{{(x-2)}^2}$ ;

 $\begin{array}{l}y"=\left[\frac{-2}{{(x-2)}^2}\right]\text{'}=-2.\left[\frac{1}{{(x-2)}^2}\right]\text{'}\\ =-2.\frac{-1}{{(x-2)}^4}.\left[{(x-2)}^2\right]\text{'}\\ =\frac{2}{{(x-2)}^4}.2(x-2)=\frac{4}{{(x-2)}^3}\end{array}$