Symbols can be anything that represents something else as a placeholder. Independent variables can be manipulated in a problem, while the dependent variables depend on the independent variables' values, and thus respond, or react to them. The domain is typically the scope of values that the independent variables, or typically the x value, in an x and y coordinate system, take on. The range is typically the scope of values that the dependent variable, or y value takes on. The domain and range symbols are typically denoted as such: (-inf, 5)U(5, inf), for example, or -inf<x<5 U 5<x<inf, or -inf<y<5 U 5<y<inf. The U denotes the "union" symbol, meaning that the range or domain could be (-inf, 5) OR (5, inf), in the case we mentioned. An example of the domain taking on these values would be the function y=5/(x-5). In this case, the function cannot take on the x value 5, or the function would "blow up", because it is undefined to divide by 0.