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Feodalherren
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Homework Statement
[itex]f(x,y) = x^{2}+y^{2}-2x[/itex], D is a closed triangular region with vertices (2,0) (0,2) and (0,-2).
Find the absolute max and min of f on D.
Homework Equations
Hessian matrix.
The Attempt at a Solution
Taking the second partials I end up with the system of equations
2x-2=0
2y=0
Adding these two I get y = 1 - x
Then looking at the domain I plug in x=0 and x=2 and get my y values and my CP:s come out as
(0,1) and (2, -1)
The Hessian comes out as 4.
(I'm not showing all the work because it's simple stuff but takes forever to write down in itex.)
Since the Hessian is positive I know we're looking at min or max points, not saddles. Now the second partial of f with respect to x is 2, always positive. Therefore I conclude that both points are global minimums.
Wrong.