alone11
幼苗
共回答了13个问题采纳率：84.6% 举报
应该是7/12不是8/12
1/3-7/12+9/20-11/30+13/42-15/56
=1/3-(3+4)/12+(4+5)/20-(5+6)/30+(6+7)/42-(7+8)/56
=1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=-1/8
原式
=(1/3-8/12+9/20-11/30+13/42-15/56)*2^3-(-2）^100*0.25^50
=(-1/8)*8-(4）^50*(1/4)^50
=-1-(4*1/4)^50
=-1-1
=-2
1年前
1
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