यदि `(5+9+13+.......n" पद")/(7+9+11+.......(n+1)" पद")=(17)/(16)` है, तब n बराबर है

Options

A. 7
B. 12
C. 8
D. 15

Answer

A

Explanation

`(5+9+13+......." पद ")/(7+9+11+.......(n+1)" पद ")`
`implies((n)/(2)[2xx5+(n-1)4])/((n+1)/(2)[2xx7+(n+1-1)2])=(17)/(16)`
`implies(n[4n+6])/((n+1)(2n+14))=(17)/(16)`
`implies(n(2n+3))/((n+1)(n+7))=(17)/(16)`
`implies(2n^(2)+3n)/(n^(2)+8n+7)=(17)/(16)implies?=32n^(2)+48n`
`=17n^(2)+136n+119`
`implies15n^(2)-88n-199=0`
`implies(n-7)(15n+17)=0impliesn=7`