Put the three terms in second expression under a common denominator and you'll get the first.

The process of going form the first to the second is a bit more difficult, but it's called breaking a fraction intopartial fractions.

You basically do it by establishing an equation like:

,

then multiply by the denominator to get:

Expand:

and compare terms on each side.

Get and , so .

Therefore

This process can be repeated on the remaining fraction:

.

Multiply to get:

.

Compare terms again, and this time get , and .

Put it all together: