Question

Bacteria quadruples on a daily basis. After the first day, there were 50 bacteria. Using the general exponential equation an=a1⋅rn−1
, what value would represent a1
?

Answer 1

a1 = 50.

Reason: the formula a_n = a1·r^{n−1} takes n=1 for "after the first day," so a_1 equals the amount then (50). Here r = 4. (If you meant the count before day 1, that would be 50/4 = 12.5.)