Which of these statements is true for f(x)=5*(6)^x?
a. the domain of f(x) is x> 0.
b. the y-intercept is (0,1).
c. it is always decreasing.
d. the y-intercept is (0,5).

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb