Find the sum of n terms of series ` 2.4 + 6.8 + 10.12+.....`

Explanation

when a=2,d=4

`a_n`=2+(n-1)4=4n-2

When a=4,d=4

`a_n`=4+(n-1)4=4n

`T_n=(4n-2)(4n)=8[2n^2-n)`

`S_n=sumT_n=sum16n^2-8n`

`(16n(n+1)(2n+1))/6-(8n(n+1))/2`

`(8*n(n+1))/2[(2(2n+1))/3-1]`

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