# Article

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Keywords:
half–linear differential equation; associated functional; Picone identity; conjugate points
Summary:
In this paper we study extremal properties of functional associated with the half–linear second order differential equation E$_p$. Necessary and sufficient condition for nonnegativity of this functional is given in two special cases: the first case is when both points are regular and the second is the case, when one end point is singular. The obtained results extend the theory of quadratic functionals.
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