Pasting problem for reference - I’m not understanding this part of the solution:
Why do we multiply (n-1) by d to get the last term, if the original case is an+d? Thank you!
a_2 = a_1 + d
a_3 = a_2 + d = a_1 + 2d
a_4 = a_3 + d = a_1 + 3d
\vdots
a_n = a_{n - 1} + d = a_1 + (n - 1)d