(1+78分之19 ×1)+(1+ 78分之19×2)+(1+ 78分之19×3)+ ………+(1+ 78分之19×12)怎么做
问题描述:
(1+78分之19 ×1)+(1+ 78分之19×2)+(1+ 78分之19×3)+ ………+(1+ 78分之19×12)怎么做
答
=12+19/78(1+2…+12)
=12+12*19/13
=12(1+19/13)
=264/13