For which rrr does the series ∑n=1∞(r2−1)n\sum_{n=1}^{\infty} (r^2 - 1)^n∑n=1∞(r2−1)n converge?
∣r∣<2|r| < \sqrt{2}∣r∣<2
0<∣r∣<20 < |r| < \sqrt{2}0<∣r∣<2
∣r∣<1|r| < 1∣r∣<1
r2<2r^2 < 2r2<2