Solveeit Logo
Login

Question

Question: If \(2n + 1P_{n - 1}:^{2n - 1}P_{n} = 3:5\), then n equals...

If 2n+1Pn−1:2n−1Pn=3:52n + 1P_{n - 1}:^{2n - 1}P_{n} = 3:5, then n equals

A

3

B

4

C

5

D

6

Answer

4

Explanation

Solution

(2n+1)2n(n+2)(n+1)n=35\frac { ( 2 n + 1 ) 2 n } { ( n + 2 ) ( n + 1 ) n } = \frac { 3 } { 5 }

10 (2n + 1) = 3(n2 + 3n + b)

3n2 - 11n - 4 = 0

3n2 - 12n + n - 4 = 0

(3n + 1) (n - 4) = 0

∴ n = 4.