xyz是正数且满足x+y-5z=0和x-y+z=0求(x^2-y^2)/(z^2-x^2)
问题描述:
xyz是正数且满足x+y-5z=0和x-y+z=0求(x^2-y^2)/(z^2-x^2)
rtrt
答
两式相加得:2x-4z=0
x=2z代入x+y-5z=0得y=3z
(x^2-y^2)/(z^2-x^2)=(4z²-9z²)/(z²-4z²)=5/3