[Potironette]

...Woops. It's actually
n(2a₁ + (n-1)d)/2 = n((a₁+a_n)/2)

2a₁ + a₂(n-1) - a₁(n-1) = a₁ + a_n
a₁ - a₁(n-1) + a₂(n-1) = a_n
a₁ - a₁n + a₁ + a₂n - a₂ = a_n
2a₁ - a₁n - a₂ + a₂n = a_n
a₁(2-n) - a₂(1-n) = a_n

It works now, but I'm not sure what it's saying.


Err do you mean the north of the earth is labeled north but it's actually magnetically south?