分式的加减法:实数x、y满足x^2+y^2+8x+6y+25=0,求x^2-4y^2/x^2+4xy+4y^2-x/x+2y的值.
题目
分式的加减法:实数x、y满足x^2+y^2+8x+6y+25=0,求x^2-4y^2/x^2+4xy+4y^2-x/x+2y的值.
答案
x^2+y^2+8x+6y+25 =(x+4)^2+(y+3)^2=0 则x+4=0 y+3=0 (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) =6/-10 =-3/5
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