Hi all,

I know that $\displaystyle \int1/e^{\frac{1}{2}y}dy=-2e^{\frac{-y}{2}}$

but I don't know how it's done?

I can integrate the denominator to get $\displaystyle 2e^{\frac{1}{2}y}$

but since it's under the "1" I've not seen this before, what rules does it use?

Many thanks.