For example, in studying elementary mathematics, one knows that the solution set of an equation in the form real-valued constants, with "a" and "b" not both equal to zero, forms a line in the vector space R. However, it may not always be easy to graphically depict solutions sets – for example, the solution set to an equation in the form (with "a", "b", "c", "d", and "k" real-valued constants) is a hyperplane.