00:01
Hello students, we are given that f of x, y equals to x, y.
00:07
So, first we determine fx equals to y, fy equals to x, finally fxx equals to 0 equals to fy, y also 0 and fxy equals to 1 which is equals to f of y, x.
00:29
So, the discriminant d is equals to fxx, fy, y minus fxy whole square, this implies 0 minus of 1 whole square implies minus 1 which is less than 0.
00:46
So, the critical point, so the critical point 0, 0 is a saddle point for f of x, y.
01:07
Second one is given that f of x, y is equals to x square plus y square.
01:14
So, we have fx equals to 2x, fy equals to 2y, fxx equals to 2 equals to fy, y and fxy equals to 0 equals to fy, x.
01:36
So, we have d is equals to 4 greater than 0 and also we see that fxx greater than 0.
01:45
So, we can say that the critical point 0, 0 is a local minima for the function f of x, y...