You can type that function in a graphing calculator and either see the graph or the table. If you put that function in a table, then you have to make sure that x isn't repeating itself. If you look at the graph, then you have to do the vertical line test
One way is to graph it and do the vertical line test it is not a function if we can draw a vertical line in the graph that passes through 2 points of the graph
if we graph this function, we see there is no place we can draw a vertical line and hit the line twice
