Soit \(\lambda=-\frac16\). Déterminer, parmi les séries ci-dessous,
celle qui converge.
- \(\displaystyle \sum_{n=1}^\infty\Bigl(\frac{\lambda+1}{\lambda-1}\Bigr)^n\)
- \(\displaystyle\sum_{n=1}^\infty \Bigl(\frac{1}{1-\lambda^2} \Bigr)^n\)
- \(\displaystyle \sum_{n=1}^\infty\frac{(-1)^{n+1}}{\lambda^n}\)
- \(\displaystyle \sum_{n=1}^\infty\frac{1}{n^{1+\lambda}}\)