Answer
See the graph
Work Step by Step
Given: $y=x^2-8x-20$
The x-coordinate is $x=\frac{-b}{2a}=\frac{-(-8)}{2.1}=4$
Substitute for x to find the y-coordinate:
$y=4^2-8(4)-20=-36$
Hence, the vertex is $(4,-36)$.
Make a list of values:
$x=-2 \rightarrow y=0$
$x=0 \rightarrow y=-20$
$x=8 \rightarrow y=-20$
$x=10 \rightarrow y=0$
