Bell:

Writing Formulas for Sequences (and evaluating)

For arithmetic (remember its like linear) so we change

y-y_1=m(x-x_1) into

a_n=d(n-1)+a_1

(you can distribute it into slope-intercept form if you would like)

For geometric (exponential) we changed y=a(b)^x into

a_n=a_1(r)^{n-1}