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Positive solutions of singular fourth-order boundary-value problems. (English) Zbl 1096.34012
Summary: We present necessary and sufficient conditions for the existence of positive $$C^3[0,1]\cap C^4(0,1)$$ solutions for the singular boundary value problem $x''''(t)=p(t)f(x(t)),\quad t\in(0,1);\quad x(0)=x(1)=x'(0)=x'(1)=0,$ where $$f(x)$$ is either superlinear or sublinear and $$p:(0,1)\to [0,+\infty)$$ may be singular at both ends $$t=0$$ and $$t=1$$. For this goal, we use fixed-point index results.

##### MSC:
 34B18 Positive solutions to nonlinear boundary value problems for ordinary differential equations 34B15 Nonlinear boundary value problems for ordinary differential equations 34B16 Singular nonlinear boundary value problems for ordinary differential equations
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