Question

Given the sequence 7, 14, 28, 56, ..., which expression shown would give the tenth term?

Answer 1

This is a geometric progression with 7 as the initial term and 2 the common ratio. 
The formula to find the nth term is 7 times 2 to the n-1. 
For the 10th term, n = 10 so the nth term equals 7 times 2 to the 9th power 
or 7 * 2**9 = 7 times 512 which equals 3584. 
Of your choices given above, the last one seems closest. 
Hope this answers your question!

Answer 2

Hello,

$u_{1}=7\\ u_{2}=2*7\\ u_{3}=2^{2}*7\\ u_{4}=2^{3}*7\\\\ u_{n}=2^{n-1}*7\\\\ u_{10}=2^{9}*7=3584$