DSolve[Derivative[2][y][x] == -((((a1*b1*(c1 - c2)*(c1 - c3))/(-c1 + x) + (a2*b2*(-c1 + c2)*(c2 - c3))/(-c2 + x) + (a3*b3*(-c1 + c3)*(-c2 + c3))/(-c3 + x))*y[x])/((-c1 + x)*(-c2 + x)*(-c3 + x))) - ((1 - a1 - b1)/(-c1 + x) + (1 - a2 - b2)/(-c2 + x) + (1 - a3 - b3)/(-c3 + x))*Derivative[1][y][x],y[x],x]
dsolve(diff(diff(y(x),x),x) = -((1-a1-b1)/(x-c1)+(1-a2-b2)/(x-c2)+(1-a3-b3)/(x-c3))*diff(y(x),x)-1/(x-c1)/(x-c2)/(x-c3)*(a1*b1*(c1-c3)*(c1-c2)/(x-c1)+a2*b2*(c2-c1)*(c2-c3)/(x-c2)+a3*b3*(c3-c2)*(c3-c1)/(x-c3))*y(x),y(x))