已知x.x+y.y+8x+6y+25=0,求代数式(x.x-4y.y)/(x.x+4xy+4y.y)-x/(x+2y)的值_数学解答

已知x.x+y.y+8x+6y+25=0,求代数式(x.x-4y.y)/(x.x+4xy+4y.y)-x/(x+2y)的值

人气：444 ℃　时间：2020-01-27 13:58:58

解答

x平方+8x+16 +y平方+6x+9=0(x+4)平方+(y+3)平方=0∴x+4=0 y+3=0∴x=-4,y=-3 原式=(x+2y)(x-2y)/(x+2y)平方-x/(x+2y)=(x-2y)/(x+2y)-x/(x+2y) =-2y/(x+2y) =6/(-4-6)=-3/5