The nth term, un, of a geometric sequence is given by un=3(4)^(n+1),

Question

a) Find the common ratio r

b) Hence, or otherwise, find Sn, the sum of the first n terms of this sequence ?

Answer 1

u_n=3*4^n+1, 

u_n-1=3*4ⁿ

a)Common ratio: r=u_n/u_n-1=(3*4ⁿ⁺¹)/(3*4ⁿ)=5

b) Find Sn yourself