2道数学简便计算题.

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2道数学简便计算题.2道数学简便计算题.2道数学简便计算题.1×98+1/2×(1-1/3+1/3-1/5+...+1/95-1/97+1/97-1/99)+1/2×(1/2-1/4+1/4-1/6+

2道数学简便计算题.
2道数学简便计算题.

2道数学简便计算题.
1×98+1/2×(1-1/3+1/3-1/5+...+1/95-1/97+1/97-1/99)+1/2×(1/2-1/4+1/4-1/6+...+1/96-1/98+1/98-1/100)
=98+49/99+49/200
=.
=1+1/2-3+1/6+3+1/12-5+1/20+5+1/30-7+1/42+7+1/56-9+1/72+9+1/90
=1+1-1/2+1/2-1/3+1/3+1/4-1/5-1/4+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10
=2-1/10=19/10
=1.9

1. 1254
2.3479