Question

find sum of sequence 7+77+777+.... n terms

Answer 1

sum

Answer 2

n terms

Answer 3

wait a minute..

Answer 4

7(10^n....

Answer 5

wolf says \[\sum_{k=1}^{n}\frac79[10^k-1]\]

Answer 6

http://www.wolframalpha.com/input/?i=sum&a=*C.sum-_*Calculator.dflt-&f2=7%2F9%2810^k-1%29&f=Sum.sumfunction_7%2F9%2810^k-1%29&f3=1&f=Sum.sumlowerlimit_1&f4=n&x=8&y=4&f=Sum.sumupperlimit_n&a=*FVarOpt.1-_**-.***Sum.sumvariable---.*--