问题 填空题
计算:1-
1
1+
1
1-
1
1987
=______.
答案

原式=1-

1
1+
1×1987
(1-
1
1987
)×1987

=1-

1
1+
1987
1986

=1-

1×1986
(1+
1987
1986
)×1986

=1-

1986
1986+1987

=

1987
3973

故答案为:

1987
3973

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