Answers

2015-02-08T13:03:37+05:30
A+5d=121
let a=1
1+5d=121
5d=120
d=24
a+5*24=121
a+120=121
a=1                   ------------------------------------------(i)
s11=11/2(2*1+10*24)
s11=11/2(2+240)
s11=11/2*242
s11=11*121
s11=1331    ANS

1 5 1
but after it i proved that a =1 form eq (i)
2015-02-08T13:12:28+05:30
X6=121
sn=n*center term(this is a formula to find the sum of an A.P if it's number is an odd)
=11*121=1331
1 5 1
if the n is an odd number we can use this formula. n*center term
in my ans why we cant take a=1
but yur formula is not given on internet even
you can use it in any question if n isodd
pls answer this also http://brainly.in/question/79378