First derivative test
To find the critical points of a function, the first derivative of the function is computed and set equal to zero. Next, the zeroes of this equation are solved for. If is is a rational function (, where ) the values that will cause the denominator to be equal to 0 are found. This is done because this will make the function undefined. In this case, the eqauation is not differentiable at that point. These are all of the critical numbers.