1:x^2+3xy-4y^2=0
(x-y)(x+4y)=0
x=y,x=-4y
(x+2y)分之(x-2y)=-1/3 或-3
2:,（x^2+y^2)(x^2-1+y^2)=12
令x²+y²=a
a(a-1)=12
(a-4)(a+3)=0
a=4,a=-3(舍去)
x^2+y^2=4