\[
\boxed{
{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) =- \left( {\frac {1-{\it a1}-{\it b1}}{x-{\it c1}}}+{\frac {1-{\it a2}-{\it b2}}{x-{\it c2}}}+{\frac {1-{\it a3}-{\it b3}}{x-{\it c3}}} \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) -{\frac {y \left( x \right) }{ \left( x-{\it c1} \right)  \left( x-{\it c2} \right)  \left( x-{\it c3} \right) } \left( {\frac {{\it a1}\,{\it b1}\, \left( {\it c1}-{\it c3} \right)  \left( {\it c1}-{\it c2} \right) }{x-{\it c1}}}+{\frac {{\it a2}\,{\it b2}\, \left( {\it c2}-{\it c1} \right)  \left( {\it c2}-{\it c3} \right) }{x-{\it c2}}}+{\frac {{\it a3}\,{\it b3}\, \left( {\it c3}-{\it c2} \right)  \left( {\it c3}-{\it c1} \right) }{x-{\it c3}}} \right) }=0}
\]