Evaluate the expression 20 miles walked

Three coins are flipped. what is the probability that there will be at least two tails?

1- what do you think the product of a nonzero rational number and an irrational number is? is it rational or irrational? make use of variables, the closure property of integers, and possibly a proof by contradiction to prove your hypothesis.2- why do we have to specify that the rational number must be nonzero when we determine what the product of a nonzero rational number and an irrational number is? if the rational number were 0, would it give us the same result we found in the first question?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?