Given the sequence 7, 14, 28, 56, which expression shown would give the tenth term? 7^10 7•2^10 7•2^9

Each term is 2 times the previous
geometric series

an=a1(r)^(n-1)
an=nth term
a1=first term
n=which term
r=common ratio

common ratio is 2
first term is 7
n=10

so
7(2)^(10-1)
7(2)^9

last option is the answer