# Article

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Keywords:
singular mixed boundary value problem; positive solution; lower function; upper function; convergence of approximate regular problems
Summary:
We study singular boundary value problems with mixed boundary conditions of the form $(p(t)u^{\prime })^{\prime }+ p(t)f(t,u,p(t)u^{\prime })=0, \quad \lim _{t\rightarrow 0+}p(t)u^{\prime }(t)=0, \quad u(T)=0,$ where $[0,T]\subset {\mathbb{R}}.$ We assume that ${\mathbb{R}}^2,$ $f$ satisfies the Carathéodory conditions on $(0,T)\times$ $p\in C[0,T]$ and ${1/p}$ need not be integrable on $[0,T].$ Here $f$ can have time singularities at $t=0$ and/or $t=T$ and a space singularity at $x=0$. Moreover, $f$ can change its sign. Provided $f$ is nonnegative it can have even a space singularity at $y=0.$ We present conditions for the existence of solutions positive on $[0,T).$
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