SOLUTION: Hi there, Can someone please help me with this question. find the quadratic function y=ax^2+2x+c find the value of a and c so that 2 becomes the maximum value at x=1. Thanks

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: Hi there, Can someone please help me with this question. find the quadratic function y=ax^2+2x+c find the value of a and c so that 2 becomes the maximum value at x=1. Thanks       Log On


   



Question 1182226: Hi there,
Can someone please help me with this question.
find the quadratic function y=ax^2+2x+c find the value of a and c so that 2 becomes the maximum value at x=1.
Thanks

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
For the graph of
y=ax%5E2%2B2x%2Bc
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

y=ax%5E2%2B2x%2Bc
2=a%281%29%5E2%2B2%281%29%2Bc
2=a%2B2%2Bc
0=a%2Bc

The formula for the x coordinate of the vertex is:

-b%2F%282a%29
So
-2%2F%282a%29=1
-2=2a
-1=a

Substitute -1 for a in

0=a%2Bc
0=-1%2Bc
1=c

To check, substitute -1 for a and 1 for c in

y=ax%5E2%2B2x%2Bc
y=-1x%5E2%2B2x%2B1
y=-x%5E2%2B2x%2B1

Then graph:

 

Edwin