Please can you prove this?
1+3+3^2+⋯⋯⋯⋯3^(n-1)= (3^n-1)/21+3+32+⋯⋯⋯⋯3n−1=3n−12
1 Answer
Apr 22, 2018
See explanation
Explanation:
We want to prove
1+3+3^2+...+3^(n-1)=(3^n-1)/2
Let us call
S=1+3+3^2+...+3^(n-1)
Multiply both sides by 3
3S=3+3^2+...+3^(n-1)+3^n
So by the definition of
3S=(S-1)+3^n
=>2S=3^n-1
=>S=(3^n-1)/2
Or
1+3+3^2+...+3^(n-1)=(3^n-1)/2