Suppose that are independent random variables, each being uniformly distributed over
(a) What is the joint cumulative distribution function of
(b) What is the probability that all the roots of the equation are real?
Let x,y,z in
The cdf of (A,B,C) is
But since A,B,C are independent, the probability of the intersection is the product of the probabilities
So the cdf is
And since you certainly know the cdf of a uniform distribution, you'll be able to answer the question...
You have to find
Try to understand that...