If a → power series → converges for some nonzero value x0, then it converges absolutely for any value of x, for which |x| < |x0|.
If a power series → diverges for some nonzero value x0, then it diverges for any value of x, for which |x| > |x0|.
See also: Named after the Norwegian mathematician Niels Henrik Abel (1802-1829); → theorem.