Also S″(x) = 4 > 0, for all x and so S″(10) > 0 Therefore, by second derivative test, x = 10 is the point of local minima of S Thus, the
distance of R from A on AB is AR = x =10 m Example 25 If length of three sides of a trapezium other than base are equal to 10cm,
then find the area of the trapezium when it is maximum