SOLUTION: fx)=-x^2+8x=7 find the maximum y-value on the graph of y=f(x) x=5? y=22? i'm pretty positive those the x, y are correct on my calculator.

Algebra ->  Rational-functions -> SOLUTION: fx)=-x^2+8x=7 find the maximum y-value on the graph of y=f(x) x=5? y=22? i'm pretty positive those the x, y are correct on my calculator.       Log On


   

Question 678514: fx)=-x^2+8x=7
find the maximum y-value on the graph of y=f(x)
x=5? y=22?
i'm pretty positive those the x, y are correct on my calculator.

Answer by fcabanski(1391) About Me  (Show Source):
You can put this solution on YOUR website!
The function is -x%5E2+%2B8x+-7. That means the function opens down and has a maximum value at x=(-b/2a) where a = -1 and b =8. Remember these functions are of the form ax^2 +bx +c


x = -8/2(-1) = -8/-2 = 4.


The y value when x=4 is -(4^2) +8(4) -7 = -16 +32 -7 = 9

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