2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/222510In this paper, we obtain the general solution and the stability result for the following functional equation in random normed spaces (in the sense of Sherstnev) under arbitrary $t$-norms $$f(2x+y)+f(2x-y)=4[f(x+y)+f(x-y)]+2[f(2x)-4f(x)]-6f(y).$$11 pagesFunctional Analysis46S40, 39B72, 54E40.text