Question

Find the value of n such that :

nP5 = 42nP3 , n > 4

Permutation nd combination

Answer 1

Hey mate here is your answer :

• n(n-1) (n-2) (n-3) (n-4) = 42 n(n-1) (n-2)

• (n-3) (n-4) = 42

• n(n-4) -3(n-4) = 42

• n² - 7n = 42

• n² - 7n - 30 = 0

= by splitting middle the term the given equation which earlier form is as the factor are:

• (n+3) (n-10) = 0

• n = 10 because n cannot be nagative .

Thus the value of n is 10.

Answer 2

Heya ___

Solution is here ____

n ( n-1) (n-2) ( n-3) (n-4) = 42n(n-1)(n-2)

(n-3) (n-4) = 42

n(n-4) -3 (n-4) = 42

n^2 -7n = 42

n^2 - 7n -30 = 0

By splitting middle term...

(n-10) ( n+3) =>0

n= 10 , -3

So -ve value can't be taken so n=10..

Thank you