Question Number 37355 by math khazana by abdo last updated on 12/Jun/18
$$\:{let}\:\Sigma\:{a}_{{n}} {x}^{{n}} \:\:\:{with}\:{radius}\:{of}\:{convergence}\:{R} \\ $$$${prove}\:{that}\:{R}\:=\:\frac{\mathrm{1}}{{lim}_{{n}\rightarrow+\infty} \:{sup}^{{n}} \sqrt{\mid{a}_{{n}} \mid}}\:\:. \\ $$