Which of these is an example of a random sample?

A.
A phone plan company surveys people on the beach to see how well they are receiving service, and uses this information in future advertising.

B.
Customers buying a new cell phone are surveyed about cell phone plans.

C.
Every twentieth caller to an independent radio station receives tickets to a concert.

D.
A phone survey is conducted using twenty names randomly taken from the phone book.

What are the solutions to the equation 4x2+3x=24-x

1- is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis. 2- 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. 3- 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 part b?

Select the margin of error that corresponds to the sample mean that corresponds to each population: a population mean of 25, a standard deviation of 2.5, and margin of error of 5%