- nC7 = nC9, find the value of "n"
- nCn-4 = 15, find "n"
Dear Student,
Q1)
nC7 = nC9
9! (n - 9)! = 7! (n - 7)!
9 x 8 x 7! (n - 9)(n - 8)(n - 7)! = 7! (n - 7)!
72 (n - 9) (n - 8) = 0
(n - 9) (n - 8) = 0
n = 8 , 9
Q2)
nCn-4 = 15
= 15
= 15
= 15
n (n - 1)(n - 2)(n - 3) = 15 x 4!
n (n - 1)(n - 2)(n - 3) = 15 x 24
n (n - 1)(n - 2)(n - 3) = 360
n (n - 1)(n - 2)(n - 3) = 6 x 5 x 4 x 3
Therefore, n = 6
Regards
Q1)
nC7 = nC9
9! (n - 9)! = 7! (n - 7)!
9 x 8 x 7! (n - 9)(n - 8)(n - 7)! = 7! (n - 7)!
72 (n - 9) (n - 8) = 0
(n - 9) (n - 8) = 0
n = 8 , 9
Q2)
nCn-4 = 15
= 15
= 15
= 15
n (n - 1)(n - 2)(n - 3) = 15 x 4!
n (n - 1)(n - 2)(n - 3) = 15 x 24
n (n - 1)(n - 2)(n - 3) = 360
n (n - 1)(n - 2)(n - 3) = 6 x 5 x 4 x 3
Therefore, n = 6
Regards