First verify it holds for n=1
then you are allowed to assume it holds for n and you can start with the induction step
for n+1 instead of inserting it into the equation, add it to both sides and transform it to the original formula to proof its equality
this equals the original formula if you had inserted n+1, proving the correctness
then you are allowed to assume it holds for n and you can start with the induction step
for n+1 instead of inserting it into the equation, add it to both sides and transform it to the original formula to proof its equality
this equals the original formula if you had inserted n+1, proving the correctness