Answer:
The answer is

Explanation:
From the question
is inversely proportional to
is written as

where k is the constant of proportionality
When
= 4
= 9
Substituting the values into the formula
we have

cross multiply
k = 4 Ă— 9
k = 36
So the formula for the variation is
= - 72
That's

Simplify
We have the final answer as

Hope this helps you