七年級數學

2022-06-23 09:55:08 字數 706 閱讀 9997

1樓:匿名使用者

(1+1/2+1/3+1/4)*(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4)

=(1+1/2+1/3+1/4)*(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4)*(1/2+1/3+1/4)-1/5*(1/2+1/3+1/4)

=(1+1/2+1/3+1/4)*1/5-1/5*(1/2+1/3+1/4)

=1/5

2樓:匿名使用者

0.2http://www.

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3樓:張之航

設a=(1+1/2+1/3+1/4)則原式為:

a*(a+1/5-1)-(a+1/5)*(a-1)=(a+1/5)*a-a-(a+1/5)*(a-1)=(a+1/5)*(a-a+1)-a

=a+1/5-a

=1/5