The Domain is the list of all allowable x values. Sometimes, equations have x values that can't be used. Here are a couple of examples:
1/x - since we can't divide by 0, x!=0
sqrtx - since we can't get real number solutions to a negative number under the square root sign, we tend to say that we can't have negative values, and so x>=0
In our case, there are no values of x that are disallowed. And so any real value can be an x value, or
x in RR - which says x can be any real value
The Range is the list of all values arising from the domain (which in this case are the y values).
In our case, when x is large, so will y. When x is a large negative, so will y. In fact, we can arrive at any value y by picking the correct value of x. And so we can say:
y in RR
And we can see this in the graph:
graph{x+3}
