I have been stuck on this for a few hours (actually a few days). I can't find much useful information on the web that has made it any clearer.
Suppose that a firm’s production function of output Q is a function of two inputs, labour (L) and capital (K) and can be written Q = 25LK.
Letting the wage rate for labour be w and the price of capital be r, what is the equation for the firm’s demand for labour?
I understand that the answer is L=√(rQ/25w) but I don't know how to get there.