The sum of 19 terms of an A.P whose nth term is 2n+1 is
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Answered by
30
399 is the answer.
find the sequence by substituting 1,2,3 values in nth term and find C.D and substitute in Sn formula n/2(2a+( n -1) D) by putting n= 19. and u get the answer
find the sequence by substituting 1,2,3 values in nth term and find C.D and substitute in Sn formula n/2(2a+( n -1) D) by putting n= 19. and u get the answer
Answered by
6
Answer:
399
Step-by-step explanation:
1st term=2(1)+1=3
2nd term=2(2)+1=5
d=5-3=2
Sn=n/2[2a+(n-1)d]
=19/2[2(3)+18(2)]
=19/2(42)
=19×21
=399
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