The derivative of $f ( x ) = \sqrt { x - 4 }$ at x = 8 is
A) $- \frac { 1 } { 8 }$
B) $- \frac { 1 } { 4 }$
C) $- \frac { 1 } { 2 }$
D) $\frac { 1 } { 4 }$
E) $\frac { 1 } { 8 }$

Question

Quizplus · Accepted Answer

The derivative of $f(x) = \sqrt{x - 4}$ can be found using the chain rule. The derivative is $f'(x) = \frac{1}{2\sqrt{x - 4}}$. Substituting $x = 8$ gives $f'(8) = \frac{1}{2\sqrt{8 - 4}} = \frac{1}{2\sqrt{4}} = \frac{1}{4}$.

The Derivative Of f(x)=x−4f ( x ) = \sqrt { x - 4 }f(x)=x−4​

The Derivative Of $f ( x ) = \sqrt { x - 4 }$