# Solving a second order differential equation

I'm in the second week of an Elementary Diff. Eq. course and the professor gave us an optional problem that is way beyond the scope of what we've discussed just as a challenge, and I don't know how to approach it. Any advice or related literature would be appreciated. The problem is below.

$$R\, (1+(y')^2)^\frac{1}{2}=xy'',$$ R is a rational constant. Initial conditions: $$y(a)=0, \quad y'(a)=-b/a,$$ $a, b$ are also rational constants.

Any help would be appreciated. All we've done so far is solve linear first-order problems. Thank you.

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put $y'=z$ and try to reduce order
And will i put the ${y''=Z'}$ ? – Ahmed Osama Mar 24 '14 at 12:56