Question

0.6 0.66 0.666…的通项公式

Answer 1

0.66=0.6+0.6*0.10.666=0.6+0.6*0.1+0.6*0.01………………用等比数列的公式求出即可

Answer 2

6*（10-1)/9^(n+1)

Answer 3

An=(1-0.1^n)*2/3