Answer:
D. (3. —1)
Step-by-step explanation:
Vertex of a quadratic function:
Suppose we have a quadratic function in the following format:

It's vertex is the point 
In which


Where

If a<0, the vertex is a maximum point, that is, the maximum value happens at
, and it's value is
.
Turning point of a quadratic function:
The turning point of a quadratic function is the vertex.
y = x2 — 6x + 8
This means that 
Now, we find the vertex.



(x,y) = (3,-1), and the correct answer is given by option D.
Step-by-step explanation:
A list of all possible outcomes in a given event is:
Sample space
60 miles per hour x 4 hours = 240 miles
Mr smith was 240 miles ahead of Mrs/ smith
The difference in speeds was 80 - 60 = 20 miles per hour
240 miles / 20 miles per hour = 12 hours.
It takes 12 hours to catch up.