Answer
(a) $+1.461$
(b) $-1.016$
Work Step by Step
Step-1: Let us differentiate $$F= \frac{132,400}{331\pm v}$$
$$\frac{dF}{dv}=(132,400)\frac{d}{dv}(331\pm v)^{-1}$$
$$=(132,400)\cdot(-1)\cdot(331\pm v)^{-2}\cdot(\pm 1)$$
$$\frac{dF}{dv}=-\frac{\pm132,400}{(331\pm v)^2}$$
Step-2: When $v=-30$,
$$\frac{dF}{dv}=-\frac{-132,400}{(331-30)^2}=1.461$$
Step-3: When $v=+30$,
$$\frac{dF}{dv}=-\frac{+132,400}{(331+30)^2}=-1.016$$
