Question

guys 1st questions answer fast

Answer 1

for n=1
lhs=1
rhs=1
ie. statement is true for n=1
let the statement is true for n=k
1+3+3^2+....+3^k-1=(3^k-1)/2
we will prove for n=k+1
1+3+3^2+...+3^k-1+3^k=(3^k+1)/2