Inequalities expresses the relation of being greater-than or being less-than. To introduce a bit fun, we would like to present some diagram which shows you some basic inequalities, such as x + (1/x) >= 2.

Proof Without Words: If x >0, x + 1/x >=2 A picture is worth a thousand words, even in mathematics. One example is the sum of which when multiplies equals 1.

A function is a special relation where the vertical line test is passed (you might be familiar with this result). But what is a horizontal line test. It is a test to decide whether the inverse of the function exists.

What is the horizontal line test? We have learned that if a vertical line intersect a graph more than once, then that graph is not a function. In this post, we learn about the horizontal line test and its relation to inverse functions.