Question

If f(x) varies directly with x, and f(x) = 45 when x = 9, find the value of f(x) when x = 3.

A.
5

B.
9

C.
15

D.
27

Answer 1

well the direct variation equation is

f(x) = kx

k = constant of variation so substitute f(x) = 45 and x = 9

to find the value of k.

when you get it

substitute x = 3 to find f(3)

hope it helps

Answer 2

f(x) varies directly with x
so you can write f(x)=kx where k is constant to find
also f(x) = 45 when x = 9
so 45=k*9
k=5
so relation would be f(x)=5x
now put x and find f(x)