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

2. 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.

3. 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.

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

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

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

8. 2.1 Complex Relationships
Some relationships are neither direct nor inverse.
This graph shows a non-linear relationship.

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

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