For the graph of
to have a maximum value, it must open downward which means that its leading
coefficient, a, must be negative.
y is its maximum value at the vertex when x=1, so we substitute 1 for x and 2
for y
The formula for the x coordinate of the vertex is:
So
Substitute -1 for a in
To check, substitute -1 for a and 1 for c in
Then graph:
Edwin