Question

What are the first and last terms of this geometric series

Answer 1

ANSWER

E. 10 and 640


Step-by-step explanation


The given series is


`\sum_(i=1)^45 * 2^(2i-1)`


To find the first term of the series we substitute i=1 to get,



`a_1 = 5 * {2}^(2 * 1 - 1)`



`a_1 = 5 * {2}^( 1) = 10`



For the last term of the series, we substitute i=4 to obtain,


`a_4 = 5 * {2}^(2 * 4 - 1)`



`a_4 = 5 * {2}^(7)`



This implies that,



`a_4 = 5 * 128 = 640`


Therefore the correct answer is E