In the previous section, we learned that functions passed the vertical line test. There is another way to classify functions which pass the horizontal line test. A function passes the horizontal line test if we draw a horizontal line anywhere in the domain of , and that line crosses in at most one or less points. If a function passes the horizontal line test then we call it one-to-one, or 1-1.
In addition to being classified as one-to-one, we
written in the form
There is one last classification of functions we are
going to talk about. A function is an even function if f(x)=f(-x).
This might be impossible you say, but take the function we just worked
is an even function. x squared is equal -x squared. So f(x) is an even function. A function is odd if f(-x)=-f(x). Take for example the function f(x) = x.