Problem 4 Consider the following function
fdefined for all
xand
yby
f(x,y)=2(1-a^(2))x^(2)y^(2)-3x^(2)-3y^(2)+2axy+4where
ais a constant in
-1,1. (a) Show that for
a=+-1,fhas only one stationary point. (b) Classify the point found in (a). (c) Show that for all
ain[-1,1], if
(x,y)is a stationary point, then
x^(2)=y^(2). (Hint: consider
{:xf_(x)^(')(x,y)-yf_(y)^(')(x,y).)