Question

如果m不等于n,(9m+n)/(9n+m)=(m+1)/(n+1),则m+n=?”

Answer 1

(9m+n)/(9n+m)=(m+1)/(n+1)

(9m+n)(n+1)=(9n+m)(m+1)

9mn+9m+n²+n=9mn+9n+m²+m

9m+n²+n=9n+m²+m

m²-n²=8m-8n

(m+n)(m-n)=8(m-n)

m≠n则m-n≠0

两边除以m-n

m+n=8