Question

2. What is the value of r if
P (5, r)=P (6, r- 1)?
on
r​

Answer 1

Answer:

Please find the attachment

Answer 2

Answer:

4

Step-by-step explanation:

P(5,r)=P(6,r-1)

We know that P(n,r) = n!/(n-r)!

=> 5!/(5-r)! = 6!/(6-r+1)!

=> (7-r)!/(5-r)! = 6!/5!

=> (7-r)(6-r)(5-r)!/(5-r)! = 6×5!/5! (n!=n.(n-1)! )

=> (7-r)(6-r) = 6

=> r^2 - 13r + 36 = 0

=> (r-9)(r-4) = 0

Hence r = 4,9

here 9 is not possible as it has to strectly follow n>=r

so ,. r=4