Now that you have used the permutation formula, you may be asked to solve equations where n or r needs to be calculated. The ability to simplify and work with factorial expressions is important.

 

In Lesson 1 you practised expanding a factorial expression that included the variable n. The ability to expand factorial expressions helps to simplify expressions.

 

Simplify

 

Expand both the numerator and denominator.

 

 

The only factor that did not divide out of the numerator and denominator was the n.

 

Self-Check 4

 

Simplify . Answer