A+AA﹢AAA﹢A﹢AA﹦1080 求A﹦

计算a+aa+aaa+……+aa…a(n个a)的值a+aa+aaa+……+aa…a(n个a) =a(1+11+111+……+11…1(n个1)) =a*[(10-1)/9+(100-1)/9+……+(10^n-1)/9] =a*[(10+100+……+10^n)/9-n/9] =...