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solve The Arithmetic series
1.Find the sum of the first 40 terms of the sequence 3,6,9,12...​

Sagot :

HIMEBANDIOLAIN

Step-by-step explanation:

an=n/2[2a1+(n-1)d]

sn= 40/2[2(3)+(40-1)3]

=20[6+(39)3]

=20[6+117]

=20(123)

sn=2,460

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