sry it's me with another question again. my test is coming up and my teacher is giving us all these challenge problems to prepare.

The sum of the first n terms in a certian arithmetic sequence is given by Sn = 3n^2 - n. Show that the nth term of the sequence is given by an = 6n - 4.

so i have this so far:

S_n = (n/2)(a1 + a_n) = 3n^2 - n

i then solved for (a1 + a_n) = 6n - 2

i also have the equation a_n = a1 + d(n-1)

i have tried solving for a_n, a1, and d using these equations but i'm not getting anywhere. Please help me.