On eigenvalue intervals of higher-order boundary value problems with a sign-changing nonlinear term

In the paper, we shall consider the boundary value problem {u(n)+λa(t)f(t,u,u′,u″,u(3),…,u(n−2))=0,n≥2,t∈(0,1),u(i)(0)=0,0≤i≤n−3,αu(n−2)(0)−βu(n−1)(0)=0,γu(n−2)(1)+δu(n−1)(1)=0 where λ>0, α,β,γ and δ are constants satisfying α, γ>0 and β,δ≥0. Intervals of λ are determined to ensure the existence of a positive solution of the boundary value problem according to the signs of a(t) and f.