Question

If $f\left(x\right)=x+2$, then $f^{\prime }\left[f\right(x\left)\right]$ at $x=4$ is.

• A. $8$
• B. $1$
• C. $4$
• D. $5$

Answer 1

The correct option is B $1$

Given, $f\left(x\right)=x+2$
On differentiating, we get $f^{\prime }\left(x\right)=1$
$\therefore f^{\prime }\left[f\right(x\left)\right]=f^{\prime }(x+2)=1$
At $x=4,f^{\prime }\left(6\right)=1$