a.b满足ab不等于0,且a/(1+a)+b/(1+b)=a+b/1+a+b,求a+b的值
问题描述：
a.b满足ab不等于0,且a/(1+a)+b/(1+b)=a+b/1+a+b,求a+b的值
答
a+b=-2
等价公式：a+b+2ab/a+b+ab+1=a+b/a+b+1
a=b=c;ab=d
c+2d/c+d+1=c/c+1
乘开：c.c+dc+c=c+c.c+2d+2dc
-2d=dc,d不等于0
c=-2