Answers are grounded in this paper and cite their sources.
In this paper, we investigate Hyers-Ulam-Rassias stability of a functional equation {align*} f(&x +ky) + f(x-ky) - k^2f(x+y) - k^2f(x-y) & +2(k^2-1)f(x)+ (k^2+k^3)f(y)+ (k^2-k^3)f(-y)-2f(ky)=0. {align*}
No takes yet. Share an insight, caveat, or question.
Yang-Hi Lee (2020) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: