Let ak= 3^k,
a/ which type of sequence is ak and write out a formula for the value of a1+a2+...+an.
b/ which type of sequence is bk and write out a formula for the value of b1+b2+...+bn.
c/ write out formula for c1+c2+...c10.
I am very unsure about how to answer this question.. can somebody help me please?