It's all here:
http://i39.tinypic.com/fp9mr7.jpg
It's all here:
http://i39.tinypic.com/fp9mr7.jpg
If you have a fraction like $\displaystyle \frac{m}{n}$ , it is the same as
$\displaystyle \frac{1*m}{0.5*\frac{n}{0.5}}$
Now split into a product of fractions and write the 0.5 and $\displaystyle \frac{1}{2}$, to get:
$\displaystyle \frac{1}{\frac{1}{2}} \frac{m}{\frac{n}{\frac{1}{2}}}$
Note that $\displaystyle \frac{1}{\frac{1}{2}}$ is 2 and can be pulled in front of the limit sign since it is a constant.
That's all we're doing. I hope this helps.