已知x^2-y^2=4xy,求(x^4+y^4)/(xy)^2的值
问题描述:
已知x^2-y^2=4xy,求(x^4+y^4)/(xy)^2的值
答
(x^2-y^2)^2=(4xy)^2 x^4+y^4-2(xy)^2=16(xy)^2 x^4+y^4=18(xy)^2
(x^4+y^4)/(xy)^2=18