Abstract
By use of the concavity of solution for an associate boundary value problem, existence criteria of positive solutions are given for the Dirichlet BVP (Φ(u'))'+λa(t)f(t,u)=0, 0<t<1, u(0)=0=u(1), where Φ is odd and continuous with 0<l1≤((Φ(x)−Φ(y))/(x−y))≤l2, a(t)≥0, and f may change sign and be singular along a curve in [0,1]×ℝ+.