已知:x2+4x+y2-6y+13=0,求(x-2y)/(x²+y²)
问题描述:
已知:x2+4x+y2-6y+13=0,求(x-2y)/(x²+y²)
答
x2+4x+y2-6y+13=0,求(x-2y)/(x²+y²)
x²+4x+4+y²-6y+9=0
(x+2)²+(y-3)²=0
x+2=0 y-3=0
∴x=-2 y=3
∴(x-2y)/(x²+y²)
=(-2-2*3)/(4+9)
=-8/13