I have a question regarding the Dividend-discount model with constant growth.

For that model we have the following formula:

Obviously the equation is undefined when they are equal to each other, and if growth is greater than cost of capital, then P becomes negative and that doesn't really make sense. So I have the following two questions...

1. Does the dividend discount model work if growth is equal or greater than cost of capital - in some modified way? Or do we have to assume that g is always less than r for the model to work?

2. If the dividend discount model can't be used, what other model will we use when growth is greater than cost of capital? If we are looking to calculate either P or Div.

DiUN+1 PN re-9 Te