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Math Help - Lagrange Problem

  1. #1
    Junior Member
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    Lagrange Problem

    Can someone please check if i have the right answer?

    Use Lagrange multipliers to find max/min values of

    f(x,y) = 3x+y

    subject to the constraint:

    5x^2+2xy=4

    I got max at (2,-4) with a value of 2

    min at (-2,4) with a value of -2


    I have gone through the problem heaps and keep getting that answer. But when i graph the two functions on a graphing program these points don't look like the max/min values of the intersections...

    Please if anyone could help that would be great, thanks!
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by mathswannabe View Post
    Can someone please check if i have the right answer?

    Use Lagrange multipliers to find max/min values of

    f(x,y) = 3x+y

    subject to the constraint:

    5x^2+2xy=4

    I got max at (2,-4) with a value of 2

    min at (-2,4) with a value of -2


    I have gone through the problem heaps and keep getting that answer. But when i graph the two functions on a graphing program these points don't look like the max/min values of the intersections...

    Please if anyone could help that would be great, thanks!
    They are local exterema, x=+2 gives a local minimum, and x=-2 a local maximum, but neither is a global maximum or minimum (and amusingly the local minimum is graeter than the local maximum).

    CB
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