计算 (1/11+1/21+1/31+1/41)*(1/21+1/31+1/41+1/51)-(1/11+1/21+1/31+1/41+1/51)*(1/21+1/31+1/41)
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计算 (1/11+1/21+1/31+1/41)*(1/21+1/31+1/41+1/51)-(1/11+1/21+1/31+1/41+1/51)*(1/21+1/31+1/41)
计算 (1/11+1/21+1/31+1/41)*(1/21+1/31+1/41+1/51)-(1/11+1/21+1/31+1/41+1/51)*(1/21+1/31+1/41)
计算 (1/11+1/21+1/31+1/41)*(1/21+1/31+1/41+1/51)-(1/11+1/21+1/31+1/41+1/51)*(1/21+1/31+1/41)
=(1/11+1/21+1/31+1/41)*[(1/21+1/31+1/41+1/51)-(1/21+1/31+1/41)]-(1/51)*(1/21+1/31+1/41)
=(1/11+1/21+1/31+1/41)*(1/51)-(1/51)*(1/21+1/31+1/41)
=(1/51)*[(1/11+1/21+1/31+1/41)-(1/21+1/31+1/41)]
=(1/51)*(1/11)
=1/561
(1/11+1/21+1/31+1/41)*(1/21+1/31+1/41+1/51)-(1/11+1/21+1/31+1/41+1/51)*(1/21+1/31+1/41)
=(1/11+1/21+1/31+1/41)*[(1/21+1/31+1/41+1/51)-(1/21+1/31+1/41)]-(1/51)*(1/21+1/31+1/41)
=(1/11+1/21+1/31+1/41)*(1/51)-(1/51)*(1/21+1/31+1/41)
=(1/51)*[(1/11+1/21+1/31+1/41)-(1/21+1/31+1/41)]
=(1/51)*(1/11)
=1/561
等于1/11*1/51
(1/11+1/21+1/31+1/41)*(1/21+1/31+1/41+1/51)-(1/11+1/21+1/31+1/41+/51)*(1/21+1/31+1/41)
=【1/11+(1/21+1/31+1/41)】*(1/21+1/31+1/41+1/51)-【1/11+(1/21+1/31+1/41+/51)】*(1/21+1/31+1/41)
=1/11*(1/21+1...
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(1/11+1/21+1/31+1/41)*(1/21+1/31+1/41+1/51)-(1/11+1/21+1/31+1/41+/51)*(1/21+1/31+1/41)
=【1/11+(1/21+1/31+1/41)】*(1/21+1/31+1/41+1/51)-【1/11+(1/21+1/31+1/41+/51)】*(1/21+1/31+1/41)
=1/11*(1/21+1/31+1/41+1/51)+(1/21+1/31+1/41)(1/21+1/31+1/41+1/51)-1/11*(1/21+1/31+1/41)-(1/21+1/31+1/41)*(1/21+1/31+1/41+1/51)
=1/11*(1/51)=1/561
最后一步有无可避免的两位数乘两位数
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