Proposition: Geometric Sum 

For all elements $a,b\in R$ of a unit ring $R$ and all natural numbers $n$, the following sum formula (called geomertic sum) holds:

$$(a-b)\sum_{k=0}^n a^k\cdot b^{n-k}=a^{n+1}-b^{n+1}.$$

| | | | | created: 2020-06-25 10:00:31 | modified: 2020-06-25 10:00:57 | by: bookofproofs | references: [8311]

1.Proof: (related to "Geometric Sum")