LI Jing1,2, YANG Ying1, CAO Huaixin1*
(1 College of Mathematics and Information Science,Shaanxi Normal University, Xi′an 710062, Shaanxi, China;2 Shaanxi Railway Institute, Weinan 714000, Shaanxi, China)
Abstract:
The stability of the composition functional equation T(T(x)-T(y))=T(x+y)+T(x-y)-T(x)-T(y) with a controlling function Φ(x,y) is discussed in this paper. It is proved that if E is a Banach spaces, Φ:E×E→\[0,∞) is continuous and such that the series (x)d∑∞j=12-j-1Φ(2jx,2jx) is uniformly convergent on every bounded subset of E,and F:E→E is a continuous mapping satisfying ‖F(F(x)-F(y))-F(x+y)-F(x-y)+F(x)+F(y)‖≤Φ(x,y)(x,y∈E).Then there exists a unique 2homogeneous continuous mapping T:E→E such that x∈E,F(F(x)-f(y))-F(x+y)-F(x-y)+F(x)+F(y)=0,‖T(x)-F(x)‖≤(x).
KeyWords:
stability; composition functional equation; idempotent mapping; continuity