# Thread: Lagrange Problem

1. ## 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!

2. Originally Posted by mathswannabe
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