JEE Main2016MathematicsPermutation and CombinationActual
If n + 2 C 6 n - 2 P 2 = 11 , then n satisfies the equation:
Options
- An 2 + n - 110 = 0
- Bn 2 + 2 n - 80 = 0
- Cn 2 + 3 n - 108 = 0
- Dn 2 + 5 n - 84 = 0
Correct answer
C. n 2 + 3 n - 108 = 0
Step-by-step solution
n + 2 C 6 n - 2 P 2 = 11 ⇒ n + 2   n + 1   n   n - 1   n - 2   n - 3 6   . 5   .   4   .   3 .   2 .   1   n - 2   n - 3 = 11 ⇒ n + 2   n + 1   n n - 1 = 11.10.9 . 8 ⇒ n = 9