Question

Given a power function of the form f(x)=axn, with f(3)=20 and f(9)=1620, find n and a

Answer 1

Correction: f(x)=ax^n

Answer 2

sub in the points
20 = a(3)^n (#1)
1620 = a(9)^n or
1620 = a(3)^(2n) (#2)

divide equation #2 by #1
81 = 3^n
n = 4
sub back into #1
20 = a(3)^4
a = 20/81

a=20/81 , n=4 , f(x) = (20/81)x^4

Answer 3

F (x) = 9-ax