How does one show that v(x) solves the equation Lv=f

where L is the differential operator: Lu= -(pu')'+qu=f

and v(x)= -(int from a to x) f(y)*u1(y)*u2(x)/(p(y)*W(y)) dy - (int from x to b) f(y)*u1(x)*u2(y)/(p(y)*W(y)) dy

where W(y) is the Wronskian

Thank you!!