X的2次方-Y的2次方=XY
x/y-y/x=1
(x/y-y/x)^2=1
x^2/y^2+y^2/x^2-2=1
x^2/y^2+y^2/x^2=3
X的2次方Y的负2次方+X的负2次方Y
=(x^4+y^4)/x^2y^2
=x^2/y^2+y^2/x^2
=3
X的2次方-Y的2次方=XY
x/y-y/x=1
(x/y-y/x)^2=1
x^2/y^2+y^2/x^2-2=1
x^2/y^2+y^2/x^2=3
X的2次方Y的负2次方+X的负2次方Y
=(x^4+y^4)/x^2y^2
=x^2/y^2+y^2/x^2
=3