Keep in mind that the function is decreasing before it hits that minimum.
The diagram shows the curve , where k is constant. The curve has a minimum point on the x-axis.
(i) Find the value of .
(ii) Find the coordinates of the maximum point of the curve.
(iii) State the set of values of for which is a decreasing function of .
(iii) I don't know how to get the decreasing order?!...
A calculus way of showing it is computing the derivative of f(x) and if the derivative is less than 0 then the function is decreasing.