What is the sum of the geometric sequence 2, 10, 50, ... if there are 7 terms?
Common ratio = 10/2 = 5.
First term = 2.
Sum of the first n terms of a G.S. is a(rn−1)r−1, where a is the first term and r is the common ratio.
Can you substitute a = 2, r = 5, n = 7 and try to proceed from here?
