Question

Find the sum of a 9-term geometric sequence when the first term is 4 and the last term is 1024?

Answer 1

The common ratio is 2, so the sum is
.. a1*(r^n -1)/(r -1)
.. = 4*(2^9 -1)/(2 -1)
.. = 4*511
.. = 2044

The sum of the sequence is 2044.