数学北大绿卡人教版六年级上册第20页的数学小博士怎么写?1/1987*1988+1/1988*1989+1/1989*1990+1/1990=1/1987*1988+1/1988*1989+1/1989*1990+1989/1989*1990(后两个相加)=1/1987*1988+1/1988*1989+(1+1989)/1989*1990=1/1987*1988+1/
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![数学北大绿卡人教版六年级上册第20页的数学小博士怎么写?1/1987*1988+1/1988*1989+1/1989*1990+1/1990=1/1987*1988+1/1988*1989+1/1989*1990+1989/1989*1990(后两个相加)=1/1987*1988+1/1988*1989+(1+1989)/1989*1990=1/1987*1988+1/](/uploads/image/z/8459436-12-6.jpg?t=%E6%95%B0%E5%AD%A6%E5%8C%97%E5%A4%A7%E7%BB%BF%E5%8D%A1%E4%BA%BA%E6%95%99%E7%89%88%E5%85%AD%E5%B9%B4%E7%BA%A7%E4%B8%8A%E5%86%8C%E7%AC%AC20%E9%A1%B5%E7%9A%84%E6%95%B0%E5%AD%A6%E5%B0%8F%E5%8D%9A%E5%A3%AB%E6%80%8E%E4%B9%88%E5%86%99%3F1%2F1987%2A1988%2B1%2F1988%2A1989%2B1%2F1989%2A1990%2B1%2F1990%3D1%2F1987%2A1988%2B1%2F1988%2A1989%2B1%2F1989%2A1990%2B1989%2F1989%2A1990%28%E5%90%8E%E4%B8%A4%E4%B8%AA%E7%9B%B8%E5%8A%A0%29%3D1%2F1987%2A1988%2B1%2F1988%2A1989%2B%EF%BC%881%2B1989%EF%BC%89%2F1989%2A1990%3D1%2F1987%2A1988%2B1%2F)
数学北大绿卡人教版六年级上册第20页的数学小博士怎么写?1/1987*1988+1/1988*1989+1/1989*1990+1/1990=1/1987*1988+1/1988*1989+1/1989*1990+1989/1989*1990(后两个相加)=1/1987*1988+1/1988*1989+(1+1989)/1989*1990=1/1987*1988+1/
数学北大绿卡人教版六年级上册第20页的数学小博士怎么写?
1/1987*1988+1/1988*1989+1/1989*1990+1/1990
=1/1987*1988+1/1988*1989+1/1989*1990+1989/1989*1990
(后两个相加)
=1/1987*1988+1/1988*1989+(1+1989)/1989*1990
=1/1987*1988+1/1988*1989+1/1989
=1/1987*1988+1/1988*1989+1988/1988*1989
(后两个相加)
=1/1987*1988+(1+1988)/1988*1989
=1/1987*1988+1/1988
=1/1987*1988+1987/1987*1988
=(1+1987)/1987*1988
=1/1987 复制下来!
数学北大绿卡人教版六年级上册第20页的数学小博士怎么写?1/1987*1988+1/1988*1989+1/1989*1990+1/1990=1/1987*1988+1/1988*1989+1/1989*1990+1989/1989*1990(后两个相加)=1/1987*1988+1/1988*1989+(1+1989)/1989*1990=1/1987*1988+1/
从后面往前面加,通分很容易的得知结果1987分之1