Q13 of 51 Page 18

Mark the correct alternative in the following :

If in the expansion of (1 + y)n, the coefficients of 5th, 6th and 7th terms are in A.P., then n is equal to


Given:




T5; T6& T7


Since T5 , T6 & T7 are in AP


Then; 2(T6) = T5 + T7


i.e.






⇒ 30+(n-4) (n-5)-12(n-4)=0


⇒30+n2-9n+20-12n+48=0


⇒n2-21n+98=0


⇒ (n-7) (n-14)=0


⇒n=7,14

More from this chapter

All 51 →
11

Mark the correct alternative in the following :

If in the expansion of occurs in rth term, then


 12

Mark the correct alternative in the following :

In the expansion of , the term independent of x is


 14

Mark the correct alternative in the following :

In the expansion of , the term independent of x is


 15

Mark the correct alternative in the following :

If the sum of odd numbered terms and the sum of even numbered terms in the expansion of are A and B respectively, then the value of is.