# What is the maximum value that the graph of #y=-x^2+6x-8#?

##### 1 Answer

Jul 3, 2016

You have to identify critical points first, and then check whether they are maxima or minima

#### Explanation:

If the first derivative of the function is

If the second derivative at the critical point is positive, the point is a minimum, if it is negative the point is a maximum. In this case the second derivative is