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