the sum of first eight terms of an AP is 100 and the sum of first nineteen terms is 551 .Find AP
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Answered by
3
Sum of first 8 terms =8a+28d=100
Sum of first 19 terms=19a+171d=551
Simplify
a+9d=29
2a+7d=25
On solving we get a=2 d=3
Sum of first 19 terms=19a+171d=551
Simplify
a+9d=29
2a+7d=25
On solving we get a=2 d=3
Anonymous:
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Answered by
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HERE IS YOUR ANSWER;
Sn=n/2[2a+(n-1)d] Is the sum of the n terms.
NOW FOR THE EIGHTH TERM;
S8= 8/2[2a+(8-1)d]
S8=8a+28d=100
2a+7d=25 ......1)
Now,
Similar for 19th term;
s19=a+9d=29......2)
Now using elimination method;
a=2 and d=3
HOPE it helps
Sn=n/2[2a+(n-1)d] Is the sum of the n terms.
NOW FOR THE EIGHTH TERM;
S8= 8/2[2a+(8-1)d]
S8=8a+28d=100
2a+7d=25 ......1)
Now,
Similar for 19th term;
s19=a+9d=29......2)
Now using elimination method;
a=2 and d=3
HOPE it helps
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