To find a domain and a range on a graph, you need to identify a set of possible input values (the domain) and the corresponding output values (the range).
To find the domain, you need to identify the x-values for a function and look for any restrictions, such as a value of x that may cause the function to be undefined (numbers such as 0). You’d express the domain as a set of numbers, if the function is filled with real numbers, the domain is (-∞, ∞)
The range is the y-values on the graph. You need to find the minimum and maximum y-values and consider any restrictions for the y-values like you did for the x. Then you’d express the range as an interval or a set of values.
If you’d like an example, we can consider the function f(x) = 1/x.
The function is defined for all real numbers except for x = 0. Therefore, the domain is (-∞, 0) U (0, ∞).
As for the range, when x approaches 0 from the left, f(x) goes to -∞, and as x approaches 0 from the right, f(x) goes to ∞. This would determine the range is also (-∞, 0) U (0, ∞).
I hope this helped! Good luck and have a nice day.