The expression 22+122ā1+32+132ā1+42+142ā1+...........+(2011)2+1(2011)2ā1 lies in the interval
A
(2011,201012)
No worries! Weāve got your back. Try BYJUāS free classes today!
B
(2011−12011,2011−12012)
No worries! Weāve got your back. Try BYJUāS free classes today!
C
(2011,201112)
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
D
(2012,201212)
No worries! Weāve got your back. Try BYJUāS free classes today!
Open in App
Solution
The correct option is D(2011,201112) We can write the expressions as 2011∑r=2r2+1r2−1=∑[1+2(r+1)(r−1)] =∑[1+1r−1−1r+1] Putting r=2,3,............,2011 =2010+1+12−12012−12011 =2011+12−[12012+12011] this lies between (2011,201112)