What is the first term of arithmetic progression  if   `S_n=3n^2-n` and `d=6`  ?

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Note that in arithmetic progression, n refers to the number of terms. If we set n=2, the sum of the two terms (`a_1 ` and `a_2` ) is:

`S_n = 3n^2 - n`

`S_n = 3(2)^2-2`

`S_n=10`

Replacing `S_n` with `a_1` + `a_2` , yields:

`a_1 + a_2 = 10`   (Let this be EQ1.)

Also, the d refers to the difference...

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