Question

计算：

1 2 3 +2 3 4 +3 4 5 +…+1994 1995 1996 +1995 1996 1997

3 1 3 +5 2 4 +7 3 5 +…+3989 1994 1996 +3991 1995 1997

=______．

Answer 1

1 2 3 +2 3 4 +3 4 5 +…+1994 1995 1996 +1995 1996 1997

3 1 3 +5 2 4 +7 3 5 +…+3989 1994 1996 +3991 1995 1997

=

(2- 1 3 )+(3- 1 4 )+(4- 1 5 )++(1995- 1 1996 )+(1996- 1 1997 )

(4- 2 3 )+(6- 2 4 )+(8- 2 5 )++(3990- 2 1996 )+(3992- 2 1997 )

=

1

2

．
故答案为：

1

2

．