忘记密码?新用户?注册
现有用户?登录
81. ( 1 1 ⋅ 2 ⋅ 3. ⋅ 4. + 1 2 ⋅ 3. ⋅ 4. ⋅ 5. + 1 3. ⋅ 4. ⋅ 5. ⋅ 6. + 1 4. ⋅ 5. ⋅ 6. ⋅ 7. + ⋯ ) 81 \ left(\ dfrac {1} {1 \ cdot2 \ cdot3 \ cdott4} + \ dfrac {1} {2 \ cdot3 \ cdott4 \ cdot5} + \ dfrac {1} {3 \ cdott4 \ cdot5 \ cdot6} + \DFRAC {1} {4 \ CDOT5 \ CDOT6 \ CDOT7} + \ CDOTS \右) 8.1(1⋅2⋅3.⋅4.1+2⋅3.⋅4.⋅5.1+3.⋅4.⋅5.⋅6.1+4.⋅5.⋅6.⋅7.1+⋯)
找到上面表达式的值。
问题加载......
注意加载......
设置加载......