This problem is in relation to multivariable local linearization, but I can't seem to understand what the problem is asking for!

Problem:The coefficient,

β, of thermal expansion of a liquid relates the change in the volumeV(in m3) of a fixed quantity of a liquid to an increase in its temperatureT(°C) as shown below.

(a) Letρbe the density (in kg/ m3) of water as a function of temperature. Write an expression fordρin terms ofρanddT. You can use rho forρand beta forβ.

What I've Tried/Done To Solve It:I did some research online about the relationship between density and temperature as well as Volume and temperature in terms of thermal expansion. (I'm assuming you shouldn't have to do this research to solve the problem, but I thought it might help me). I learned that Volume and temperature are directly proportional. I also learned that density and temperature are inversely proportional. At least I *think* this is true, and I'm not exactly sure how it would all relate to thermal expansion. Anyway, I noticed that the equation involving volume above showed a directly proportional relationship, using

βas a sort of proportionality constant.Based on that, I guessed that the relationship between density and temperature would look similar, but inversely proportional, like this:

dρ =(β/ρ) dT

However, this answer is wrong.

I would really appreciate any help, even if it's just to push me in the right direction. Explanations of anything you're doing would be wonderful. I'd really like to learn conceptually what these types of problems are asking for. Thank you!