Question

The function f(x) varies inversely with x and f(x)=-15 when x=30

What is the inverse variation equation?
A. f(x)= -5/x
B. f(x)= -2/x
C. f(x)= -90/x
D. f(x)= -450/x
Need help, don't understand this question in the slightest.

Answer 1

f(x) is the function that represents a given equation. It is defined more specifically by rules or conditions to satisfy the whole formula/equation.

In this case, f(x) has an inverse proportion with x (e.g. f(x) = 1/x). The second parameter says that f(x) = -15 when x is 30. Given that condition, just look for the formula, among the choices, that will result to -15 when x = 30. The answer is:

D. f(x) = -450/x

This is just -450/30 = -15