Airy-like equation with non-linear term

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I am trying to solve numerically the following equation $$y'' = xy + y^3$$ I know that for $x<0$ it can be approximately described by $y = \sqrt{-x}$. So I tried to solve it in MATLAB and mathematica with initial conditions $y(-5) = \sqrt{5},~y'(-5) = -1/(2\sqrt{5})$ but both programs failed to solve it properly. After certain iteration the step size became smaller than solver limit. Any suggestions how it can be solved?