运用上下解方法及不动点指数理论,在非齐次边界条件下讨论了三阶三点边值问题u″′(t)+a(t)f(t))=0,t∈(0,1),u(0)=λ1,u′(0)=λ2,u′(1)-au′(η)=λ3正解的存在性和不存在性,并且给出了该问题至少存在一个正解,两个正解及无正解时参数(λ1,λ2,λ3)的最优取值范围。其中(λ1,λ2,λ3)∈R3*/|0,0,0)|为参数,η∈(0,1),α∈[0,1/η)为常数,α∈С((0,1),[0,+∞)),f∈С([0,+∞),[0,+∞))。
By using the lower and upper solutions method and fixed point index theory, we study the existence and non- existence of positive solutions of nonhomogeneous boundary value problem u″′(t)+a(t)f(t))=0,t∈(0,1), u(0)=λ1,u′(0)=λ2,u′(1)-au′(η)=λ3 and given the optimal regions of (λ1,λ2,λ3) when the above problem at least exist one positive solution, two positive solutions and no positive solution, respectively. Where (λ1,λ2,λ3) ∈R3*/|0,0,0)| tare parameters, η∈(0,1),α∈[0,1/η)are constants,α∈С((0,1),[0,+∞)),f∈С([0,+∞),[0,+∞)).