The nth term of an ap is given tn =7n+1 find the sum of the 20 terms of ap
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Step-by-step explanation:
tn=7n+1
putting n=1,2,3,4,.....
AP:8,15,22,29,.....
a=8 ,d=7,Sn=n/2[2a+(n-1)d]
.=S20=20/2[2×8+19×7]
=10×[16+133]=1490
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