Hi i have an integration problem. basically i am going through an example...the equation i want to find the gen solution is shown below..i have also shown the gen solution as well...but i cant understand how they got to that answers

$\displaystyle \xi_{yy}$ + $\displaystyle (1/y)\xi_{y}$=0

The general solution is given by

$\displaystyle \xi$ = $\displaystyle A(x)\ln(y) + B(x)$

can some one explain how they got to this general soution..thanks