12+13+23+14+24+34+15+25+35+45+…+1100+2100+…+99100

12+13+23+14+24+34+15+25+35+45+…+1100+2100+…+99100.
2025-05-19 14:45:24
推荐回答(1个)
回答1:

1
2
+
1
3
+
2
3
+
1
4
+
2
4
+
3
4
+
1
5
+
2
5
+
3
5
+
4
5
+…+
1
100
+
2
100
+…+
99
100

=
1
2
+(
1
3
+
2
3
)+(
1
4
+
2
4
+
3
4
)+(
1
5
+
2
5
+
3
5
+
4
5
)+…+(
1
100
+
2
100
+…+
99
100
),
=
1
2
+1+1
1
2
+2+…+49
1
2

=(
1
2
+1
1