Find the absolute extrema of the function (if any exist) on each interval. (If an answer does not exist, enter DNE.)

Before we can determine the absolute extrema of the function, let's graph the given function first. f(x) = x² - 6x.
For the interval [-1, 6], we can see that the maximum value would be at x = -1.
Let's replace x with -1 in the function above.
[tex]\begin{gathered} f(x)=x^2-6x \\ f(-1)=(-1)^2-6(-1) \\ f(-1)=1+6 \\ f(-1)=7 \end{gathered}[/tex]Therefore, the maximum between the interval [-1, 6] is at (-1, 7).
On the other hand, looking at the interval (3, 7] in the graph, the maximum is found at x = 7. To determine the maximum point, replace "x" with 7 in the function above.
[tex]\begin{gathered} f(7)=7^2-6(7) \\ f(7)=49-42 \\ f(7)=7 \end{gathered}[/tex]Therefore, the maximum at the interval (3, 7] is at point (7, 7).