Step-by-step explanation
a way of writing subsets of the real number lines is by using intervals,
let's chec
A) closed interval
this includes the endpoints
it means a and b are part of the interval, we use the closed brackets
B)open interval
this interval is one that does not include its endpoints
it means a and b are not part of the interval
C) combinatios
so, we have the interval
it means -1 is part of the set and 12 is not part of the set
as -1 is part of the interval, we need the number equal or greater than -1