This is clearly for minimum, since
,
which is positive for a positive value of .
For a particular type of candle-power lamps, pence, pence; and it was found that and .
watts per candle-power.
Exercises X. (You are advised to plot the graph of any numerical example.) (See p. 258 for the Answers.)
(1) Find the maxima and minima of
.
(2) Given , find expressions for , and for , also find the value of which makes a maximum or a minimum, and show whether it is maximum or minimum.
(3) Find how many maxima and how many minima there are in the curve, the equation to which is
;
and how many in that of which the equation is
.