If you graph the equation (assuming that it is equal to zero), you will see that the x-intercepts are -1 and 3.
These can also be determined through the quadratic equation.
The vertex is (1,8), using -b/2a you can get the x-value of the vertex and then insert it into the equation to get the y-value.
Here's the graphical solution that confirms Anonymous' answers
https://www.desmos.com/calculator/fbm3sesyex