Math
posted by Piwo on .
A sequence is formed by adding together the corresponding terms of a geometric sequence and and an arithmetic sequence.The common ratio of the geometric sequence is 2 and the common difference of the arithmetic sequence is 2.The first term of the new sequence is 1 and the second term is 7.
Could you please help me find the third term of the new sequence.
Thank you.

AS: a+2n
GS: b*2^(n1)
a+b = 1
a+2 + 2b = 7
a + b = 1
a + 2b = 5
b = 4
a = 3
3 + 2n: 3 1 1 3 5
4*2^(n1): 4 8 16 32 64
sum: 1 7 17 35 69
Looks like 17