Suppose that a^2 varies inversely with b^3. If a = 7 when b = 4, find the value of a^2 when b = 6.
Start with
\(a^2\; \propto \;\frac{1}{b^2}\\ a^2\; = \;\frac{k}{b^2}\)
Now sub in a=7 and b=4 to get k.
Then you have the formula that you can use for any given value of a or b.