Theorem T62 If 0≤x<10 \leq x < 10≤x<1, then ∑k=0∞xk=11−x .\sum_{k=0}^\infty x^k = \frac{1}{1 - x} \; . k=0∑∞xk=1−x1. If x≥1x \geq 1x≥1, the series notation-integer-finite-summation