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anonymous

  • one year ago

At where does y=54x -9x^2 have a maximum value? Using calc, pls...?

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  1. anonymous
    • one year ago
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    take the y' and the let the equation = 0 then solve it

  2. anonymous
    • one year ago
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    y'=54-18x y'=54-18x=0 solve for x x=-54/-18=3

  3. anonymous
    • one year ago
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    now use this value (3) in y=54x -9x^2 y=54(3)-9(3)^2 =162-81=81 (3,81)

  4. Michele_Laino
    • one year ago
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    alternatively, we note that the graph of your function is a parabola like this: |dw:1433063023555:dw| whose x-coordinate of vertex is: \[\Large {x_V} = - \frac{b}{{2a}} = - \frac{{54}}{{2\left( { - 9} \right)}} = ...?\] and the y-coordinate of the vertex, is: \[\Large {y_V} = - \frac{{{b^2} - 4ac}}{{4a}} = - \frac{{{{54}^2}}}{{4\left( { - 9} \right)}} = ...?\]

  5. anonymous
    • one year ago
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    @AJ01 and @michele_laino Thanks a bunch, it means a lot :')

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