Given number: enx It is a series of species an(cx−x0)dn - power series. The radius of convergence of a power series can be calculated by the formula: Rd=cx0+limn→∞an+1an In this case an=enx and x0=0 , d=0 , c=1 then 1=n→∞lim(enre(x)e−(n+1)re(x)) Let's take the limit we find 1=e−re(x)