已知X的平方+Y的平方+8X+bY+25=0,求X的平方-4Y的平方/X方+4XY+4Y方-X/X+2Y
问题描述：
已知X的平方+Y的平方+8X+bY+25=0,求X的平方-4Y的平方/X方+4XY+4Y方-X/X+2Y
1
答
x^2+y^2+8x+6y+25
=(x+4)^2+(y+3)^2=0
则
x+4=0
y+3=0
x=-4
y=-3
(x^2-4y^2)/(x^2+4xy+4y^2)-x/(x+2y)
=[（x+2y）（x-2y）]/(x+2y)^2-x/(x+2y)
=（x-2y）/(x+2y)-x/(x+2y)
=-2y/(x+2y)
=-2*(-3)/(-4+2*(-3))
=6/-10
=-3/5