Math

Find the maximum or minimum value of function and the value of x when it occurs: -2x^2+5x+5.

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asked by Han
  1. let y = -x^2 + 5x + 5
    dy/dx = -2x + 5
    = 0 for a max of y

    2x = 5
    x = 5/2

    when x = 5/2
    y = -25/4 + 5(5/2) + 5
    = 45/4

    you should recognize y = -x^2 + 5x + 5 as a downward opening parabola ,
    the max is 45/4 when x = 5/2

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    posted by Reiny
  2. but the answer says that it's a max of 65/8 at x=5/4

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    posted by Han
  3. Correct. Reiny missed the -2x^2. Even experts trip over the details sometimes.

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    posted by Steve
  4. so can you show me the correct way to do it?

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    posted by Han
  5. wait nvm thanks for your help :D

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    posted by Han

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