ConditionThe Spectral radius of A (maximum absolute value of Eigenvalue) is less than 1, ensuring convergence of the infinite seriesAs a result, I−AI−AI−A has an inverse matrixResultsIntuitively, same as Geometric Series ∑k=0∞Ak = I+A+A2+⋯ = (I−A)−1\sum_{k=0}^{\infty} A^k \;=\; I + A + A^2 + \cdots \;=\; (I - A)^{-1}∑k=0∞Ak=I+A+A2+⋯=(I−A)−1