1 results for Let Fxyexxey 1 find fx and fy2 Set them equal
1 results for Let F(x,y)=e^x-xe^y. 1. find fx and fy.2. Set them equal to zero and slove to find the critical point. 3. Find fxx,fyy,fxy and fyx and then use them to calculate d(x,y) . 4. what have you found? local maximum,local minimum or saddle point?
Solution
F(x,y) = ex - xey
1,2) fx = ex - ey = 0
x = y
fy = -xey = 0
x = 0 => y = 0
(0, 0) is only critical point
3) fxx = ex
fyy = -xey
fxy = -ey
fyx = -ey
4) D = fxxfyy - fxyfyx = -xex+y - e2y
D(0,0) = -1 < 0
so (0,0) is a saddle point
