Question

find n if nP4 = 9 x raised to power n-1 x P3

Answer 1

Answer:

We know that,

n

P

r

=

(n−r)!

n!

Given,

n

P

4

:

n−1

P

3

=9:1

⇒

n−1

P

3

n

P

4

=

1

9

⇒

(n−1−3)!

(n−1)!

(n−4)!

n!

=9

⇒

(n−4)!

(n−1)!

(n−4)!

n(n−1)!

=9

⇒n=9