Find the sum of the first 40 terms of the as whose firsy and third terms are 15 and 21 respectively...
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hey!!!
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according to the question;
a=15
d will be =3(according to third term).
now,
Sn= 40/2[ 2 x 15 +(40-1)x 3]
= 20[ 30+117]
= 20 x 147.
= 2940.
_______________________________________________
hope it helps. ☺☺☺
_________________________________________________
according to the question;
a=15
d will be =3(according to third term).
now,
Sn= 40/2[ 2 x 15 +(40-1)x 3]
= 20[ 30+117]
= 20 x 147.
= 2940.
_______________________________________________
hope it helps. ☺☺☺
sabeaoladivepbpq9v:
Thank you so much
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