Find the sum of 7 terms of the series:11, 103, 1005,....
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a= 11, D= 103 - 11= 92
a7= n/2 {2a+ (n+1) D}
= 7/2 { 2× 11 +(7+1)×92}
= 7/2 { 22 +8×92}
= 7/2 { 22+736}
=7/2 {758}
=7×379
=2653
sum of 7 term is 2653
a7= n/2 {2a+ (n+1) D}
= 7/2 { 2× 11 +(7+1)×92}
= 7/2 { 22 +8×92}
= 7/2 { 22+736}
=7/2 {758}
=7×379
=2653
sum of 7 term is 2653
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