I'm following my notes, and I don't understand how to get from:

$\displaystyle (a^2+s^2)\frac{d\hat{y}}{ds}(s)+s\hat{y}(s)=0$

to:

separating the variables and integrating gives

$\displaystyle \int\frac{\hat{y'}(s)}{\hat{y}(s)}ds=-\int\frac{s}{a^2+s^2}ds$

can someone please explain the working that goes in between?