That there exists a pair of consecutive integers such that one of these integers is a perfect square and the other is a perfect cube

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?

Which statement about 6x2 + 7x – 10 is true?