x^2+y^2-6x-8y+25=o 求代数式(xy-3x^2)/ y^2-xy-6x^2 的值
问题描述：
x^2+y^2-6x-8y+25=o 求代数式(xy-3x^2)/ y^2-xy-6x^2 的值
答
(x-3)^2+(y-4)^2=0
x=3 y=4
(xy-3x^2)/ y^2-xy-6x^2
=[x(y-3x)]/[(y-3x)(y+2x)}
=x/[y+2x]
=3/[4+2*3]
=3/10