Neumann series
= Neumann series
{wiki}
If $a$ belongs to a unital <Banach algebra> and $\lVert a\rVert<1$, then
$$
(1-a)^{-1}=\sum_{n=0}^\infty a^n.
$$
Absolute convergence and multiplication of partial sums prove the identity.
= Neumann series
{wiki}
If $a$ belongs to a unital <Banach algebra> and $\lVert a\rVert<1$, then
$$
(1-a)^{-1}=\sum_{n=0}^\infty a^n.
$$
Absolute convergence and multiplication of partial sums prove the identity.