If you want to know the domain of a function through its graph, I simply have to "scan" the graph of the function from left to right along the X axis and see the ranges of values of the x for which it exists a value on the Y axis. In this graph it is observed that for any value of X there will be a value of Y, so that the domain of the graph function is all the real values of X
the domain of the graphed function is
x is a real number