13. Incorrect. The answer is true not false. To obtain this model it is necessary to find the conditional density function, which is defined as follows:

First of all, we have to obtain the marginal density f₁. It is obtained by fixing y and integrating with respect to x from x = y to x = 1. The result is, for 0 < y < 1:

for all other values of y, f₁(x) = 0.

The conditional density function of x is, for 0 < y < 1: