14.2 Exercise 4

(See Exercise 10 from "Problems On Random Vectors and Joint Distributions", Exercise 20 from "Problems on Mathematical Expectation", and Exercise 23 from "Problems on Variance, Covariance, Linear Regression"). $f_{X Y} \left(t , u\right) = 1$ for $0 \leq t \leq 1$, $0 \leq u \leq 2 \left(1 - t\right)$.

The regression line of Y on X is $u = 1 - t$.