(iii) Assume, 
Upon differentiating both sides and using quotient rule to get,
![\[f'(x) = \frac{{x - b - x + a}}{{{{(x - b)}^2}}}\]](https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-cb64d4f4efade79879bfe4d66379ee00_l3.png "Rendered by QuickLaTeX.com")
Therefore,
![\[f'(x) = \frac{{a - b}}{{{{(x - b)}^2}}}\]](https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-486767c212e05d4b29314320f123bb5e_l3.png "Rendered by QuickLaTeX.com")
.
For some constants a and b, find the derivative of (iii) 
(iii) Assume,
Upon differentiating both sides and using quotient rule to get,
Therefore,
.