Question

How do you evaluate 5P4?

Answer 1

`120`

Explanation:

`"using the definition for "^nP_r`

`•color(white)(x)^nP_r=(n!)/((n-r)!)`

`"where "n! =n(n-1)(n-2)...... xx3xx2xx1`

`rArr^5P_4=(5!)/((5-4)!)=(5!)/(1!)`

`[1! =1]`

`rArr^5P_4=5! =5xx4xx3xx2xx1=120`