Question

Find n if P(n, 4) = 20 P (n, 2).​

Answer 1

p(n,4)=20p(n,2)

n=7

hope this answer us helpful for u.....

Answer 2

The value of n is 7.

Step-by-step explanation:

Given : $P(n,4)=20P(n,2)$

To find : The value of n ?

Solution :

We know that, $P(n,r)=\frac{n!}{(n-r)!}$

$P(n,4)=20P(n,2)$

Substitute the formula,

$\frac{n!}{(n-4)!}=20(\frac{n!}{(n-2)!})$

$\frac{1}{(n-4)!}=20(\frac{1}{(n-2)!})$

$\frac{(n-2)!}{(n-4)!}=20$

$\frac{(n-2)(n-3)(n-4)!}{(n-4)!}=20$

$(n-2)(n-3)=20$

$n^2-5n+6=20$

$n^2-5n-14=0$

$n^2-7n+2n-14=0$

$n(n-7)+2(n-7)=0$

$(n-7)(n+2)=0$

$n=7,-2$

Reject n=-2.

The value of n is 7.

#Learn more

P (n-1,3): P(n + 1, 3) = 5 : 12. find n​

https://brainly.in/question/13777189