SOLUTION: What is the maximum value of f(x) = 3- (x+2)^2

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Question 717624: What is the maximum value of f(x) = 3- (x+2)^2
Found 3 solutions by Edwin McCravy, MathLover1, solver91311:
Answer by Edwin McCravy(20063) About Me  (Show Source):
You can put this solution on YOUR website!
f(x) = 3- (x+2)^2
We write it in vertex form

f(x) = a(x-h)² + k

f(x) = -1(x+2)² + 3
So -h = +2, so h = -2
and k = 3.

The vertex is the point (h,k) = (-2,3) which is a maximum POINT
if a is negative and a minimum POINT if a is positive.  Since
a = -1, then (-2,3) is a maximum POINT.  But you wanted the maximum
VALUE, not the maximum POINT.  The maximum VALUE is just the
y-coordinate of the maximum POINT, which is 3.

Here is the graph. Notice that it just reaches up as high as 3
on the y-axis.
 
graph%28400%2C400%2C-10%2C10%2C-10%2C10%2C3-%28x%2B2%29%5E2%29

Edwin

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
The maximum value is the vertex.
the equation for a parabola can also be written in "vertex form":
y+=+a%28x-h%29%5E2+%2B+k

you have f%28x%29+=+3-%28x%2B2%29%5E2 ...since f%28x%29+=y, you have

y=+3-%28x%2B2%29%5E2....rearrange the terms on right side
y=-%28x%2B2%29%5E2%2B3...compare to y+=+a%28x-h%29%5E2+%2B+k and you see that a=-1, h=-2 and k=3
so, vertex is at (-2,3) and it is maximum

Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


Re-arrange it so that it is in correct vertex form:



Now, knowing the negative lead coefficient indicates that the parabola opens downward, a parabola with the equation has a vertex at , and that the -coordinate of the vertex of a parabola is the extreme value of the function, you can read the maximum value of your parabola directly.

John

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