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anonymous

  • 4 years ago

The highway mileage m in miles per gallon for a compact car is approximated by m(s) = -0.025s2 + 2.45s - 30, where s is the speed in miles per hour. What is the maximum mileage for this compact car to the nearest tenth of a mile per gallon?

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  1. Mertsj
    • 4 years ago
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    This is a parabola that is concave downward since the coefficient of the s^2 term is negative. We could complete the square to find the vertex but it is probably easier to use the fact that the x coordinate of the vertex is x=-b/2a and then plug that value in to find the y coordinate of the vertex. So here we go:

  2. Mertsj
    • 4 years ago
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    \[x=\frac{-2.45}{2(-.025)}= 49\]

  3. Mertsj
    • 4 years ago
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    Now replace s in the original equation with 49 and that will be the y coordinate of the vertex.

  4. Mertsj
    • 4 years ago
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    \[y=-.025(49)^{2}+2.45(49)-30=30.025\]

  5. Mertsj
    • 4 years ago
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    Is that what you got?

  6. Mertsj
    • 4 years ago
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    So the maximum mileage is 30.0

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