Question

max and min value of 2(x^2 -y^2)-x^4+y^4

Answer 1

I think they cannot be determined, because 2(x^2-y^2) - (x^4-y^4)

hence (x^2-y^2)(2+x^2+y^2) = F

Now see, when x<y F<0 , and has actually no limit,

Similarly, for for x=y , F=0 and For x>y, F>0

So max value is infinity and minimum value is - infinity,