Determine for each x-volume wether it is in the domain of f or not

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Okay so i didn't get this problem petro bought 8 tickets to a basketball game he paid a total of $200 write an equation to determine whether each ticket cost $26 or $28 so i didn't get this question so yeahyou have a good day.

Gabrielle's age is three times mikhail's age. the sum of their ages is 40 . what is mikhail's age? __ years old