Stationary points are the points on a curve where the gradient is 0. This means that at these points the curve is flat. Usually, the gradient of a curve is always changing and so the gradient is only 0 instantaneously (unless the curve is a flat line, in which case, the gradient is always 0).
Recall the graph of . The vertex at the bottom of the curve is a STATIONARY POINT. In this case, there is a stationary point at (0,0).
Now consider the general positive quadratic in the form where . There is a stationary point at the bottom of the curve; this is called a MINIMUM. Now consider a negative quadratic of the form where . There is a stationary point at the top of the curve; this is called a MAXIMUM.
A stationary point can be found by solving , i.e. finding the x coordinate where the gradient is 0. dy/dx is found by differentiating.
Example – Find the stationary points on the curve .
Start by solving . i.e. . Factorising gives and so the x coordinates of the stationary points are x=4 and x=1. Substituting these into the y equation gives the coordinates of the stationary points as (4,-28/3) and (1,-1/3).