if sn denotes the nth term of the series 2+3+6+11+18+...... then find t50.
Answers
Answered by
2
the diff of the terms of the series are in AP and the series we get from their diff is 1,3,5...
now observe that
2
2+1=3
2+1+3=6
2+1+3+5=11
.
.
.
so the n-th term of the original series is basically sum of n-1 terms of the series (1+3+5...) +2
hence calculate sum of 49 terms of 1+3+5... which is an AP with a common diff of 2 which can easily be obtained by the formula (n/2(2a+(n-1)d)) and then add 2 to get the sum upto the 50th term=2403(calc error possible)
now observe that
2
2+1=3
2+1+3=6
2+1+3+5=11
.
.
.
so the n-th term of the original series is basically sum of n-1 terms of the series (1+3+5...) +2
hence calculate sum of 49 terms of 1+3+5... which is an AP with a common diff of 2 which can easily be obtained by the formula (n/2(2a+(n-1)d)) and then add 2 to get the sum upto the 50th term=2403(calc error possible)
zxc7:
sorry but can you please rephrase your question in a more accurate manner
i m saying that u are saying that to get the answer we first find the 49th term of the series 1,3,5,....and then add 2 to it isnt it ?????
Precisely
so i m asking that why here we are finding the 49th term and not 50th term of 1,3,5,...
and then add 2 to it
please answer
observe that the n-th term of the series 2+3+6+11 is equal to the sum upto the (n-1)th term of the series 1+3+5+7 plus 2 and hence we find the 49th term.for example the third term of the original series 6 is equal to the sum upto the (3-1)th term of the series 1+3+5+7 plus 2
ya now i got it thank you very miuch
np
Helllllllooooooooooo everyone................
Answered by
3
the diff of the terms of the series are in AP and the series we get from their diff is 1,3,5...
now observe that
2
2+1=3
2+1+3=6
2+1+3+5=11
.
.
.
so the n-th term of the original series is basically sum of n-1 terms of the series (1+3+5...) +2
hence calculate sum of 49 terms of 1+3+5... which is an AP with a common diff of 2 which can easily be obtained by the formula (n/2(2a+(n-1)d)) and then add 2 to get the sum upto the 50th term=2403
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