Final Answer
Step-by-step Solution
Specify the solving method
Evaluate the limit $\lim_{x\to a}\left(\frac{\sqrt{b^2-x}-\sqrt{b^2-a}}{x-a}\right)$ by replacing all occurrences of $x$ by $a$
Cancel like terms $\sqrt{b^2-a}$ and $-\sqrt{b^2-a}$
Cancel like terms $a$ and $-a$
$\frac{0}{0}$ represents an indeterminate form