2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/80691We prove that, for $m\ge 7$, scalar evolution equations of the form $u_t=F(x,t,u,...,u_m)$ which admit a nontrivial conserved density of order $m+1$ are linear in $u_m$. The existence of such conserved densities is a necesary condition for integrability in the sense of admitting a formal symmetry, hence integrable scalar evolution equations of order $m\ge 7$ are quasilinear.15 pages, no figuresExactly Solvable and Integrable Systemstext