Section 2-5 What Are Graphs? November 10, 2010 Page 71 & 73

What Is a Graph? A graph is a mathematical diagram that shows: one variable (dependent) on the y (vertical) axis a second variable (independent) on the x (horizontal) axis.

A graph is a simple form of model that connects two or more variables. 2.1 Reading a graph A graph is a simple form of model that connects two or more variables. Scientists use models to make and test predictions.

Kinds of Relationships Two variables may have: a strong relationship, a weak relationship, or no relationship at all.

Direct Relationships In a direct relationship, when one variable increases, the other also increases. This is also called a linear relationship.

Inverse Relationships In an inverse relationship, when one variable increases, the other decreases.

2.1 Complex Relationships Some relationships are neither direct nor inverse. This graph shows a non-linear relationship.

Linear and Non-Linear Graphs Linear graphs go in a straight line. They represent relationships with the formula y=kx

Non-Linear Graphs Non-linear graphs go in curves They usually have formulas like y=kx2