Formula Explanation
Problem as stated
Using rules of factorials, change denominators to make LCD finding easier
Find least common denominator
Add the two fractions together
Factor out the in the numerator. This is where the + k comes from.
Simplify.

As noted, this can also be written as .
--Melink14 (talk) 02:12, 26 April 2009 (UTC)Reply



Now for the second question.

Formula Explanation
The stated problem.
Write out as per the definition of combinations.
Use factorial math to simplify denominators for LCD finding
Find the LCD.
Add.
Factor out the like last time.
Basic simplification of numerator
Simplify again using rules of factorials
A simple identity to make the connection to the next part clear.
This is the final result the question was looking for.

--Melink14 (talk) 02:56, 26 April 2009 (UTC)Reply