What are stationary points and how do I find them?

If you have a differentiable function, stationary points are, by definition, those points where the derivative of the function is 0. Considering that the derivative of a function represents the rate of increase (or decrease), in a way, stationary points are where a function is flat. To find them, we simply follow the definition: compute the derivative of a function (remember that the derivative will be a function itself), set it equal to 0 and solve the equation. Then, to check if the stationary point is a minimum or a maximum, compute the value second derivative at the stationary point. If it's positive, we have a minimum, otherwise it's a maximum.