设正整数m,n,满足m<n,且1/m2+m+1/(m+1)2+(m+1)+…+1/n2+n=1/23,则m+n的值是_.
问题描述:
设正整数m,n,满足m<n,且
+1
m2+m
+…+1
(m+1)2+(m+1)
=1
n2+n
,则m+n的值是______. 1 23
答
∵
=1
n2+n
-1 n
,1 n+1
∴
+1
m2+m
+…+1
(m+1)2+(m+1)
,1
n2+n
=
-1 m
+1 m+1
-1 m+1
+…+1 m+2
-1 n
,1 n+1
=
-1 m
=1 n+1
=1 23
,22 23×22
∴m=22,n+1=23×22=506,n=505,
m+n=527.