Imagine the graphs of the sequences generated by these recursive formulas. Describe each graph using exactly three of these terms: arithmetic, decreasing, geometric, increasing, linear, nonlinear, shifted geometric.
a. u0 = 450, un = a · un-1 where n ≥ 1 and 0 < a < 1
b. u0 = 450, un = b + un-1 where n ≥ 1 and b < 0
c. u0 = 450, un = un-1 · c where n ≥ 1 and c > 1
d. u0 = 450, un = un-1 + d where n ≥ 1 and d > 0