Download the app

Questions  

If (x)<1, and rth term of a series is 1 + x+x2++xr1, then sum to n terms of the series is

Remember concepts with our Masterclasses.

80k Users
60 mins Expert Faculty Ask Questions
a
n+(n+1)x−xn+1(1−x)2
b
n−(n+1)x+xn+1(1−x)2
c
(n+1)x−xn+1−n(1−x)2
d
n−(n+1)x−xn+1(1−x)2

Ready to Test Your Skills?

Check Your Performance Today with our Free Mock Tests used by Toppers!

detailed solution

Correct option is B

tr=1+x+x2+…xr−1=1−xr1−xNow, ∑r=1n tr=∑r=1n 1−xr1−x=n1−x−11−x∑r=1n xr=n1−x−11−xx1−xn1−x=1(1−x)2n−nx−x+xn+1=1(1−x)2n−(n+1)x+xn+1


Similar Questions

(6666)2+(8888) is equal to

n digits         n digits     


whats app icon
phone icon