Page 126 - Algebra 1

Example
1
Graphing Ordered Pairs on a Coordinate Plane
Graph each ordered pair on a coordinate plane. Label each point.
Hint
When graphing a point, always move left or right first.
a. (4, 2) SOLUTION
Point (4, 2) is located in the first quadrant, 4 units to the right of the origin and 2 units above the horizontal axis.
b. (-3, 0) SOLUTION
(-3, 0)
Point (-3, 0) is on the x-axis. It is located 3 units to the left of the origin.
4
y
(4,
2)
4
y
x
O
x
O
-4
4
-4
4
-4
-4
When there is a relationship between two variable quantities, one variable is the independent variable and the other is the dependent variable.
The dependent variable always depends on what value is chosen for the independent variable.
Identifying Independent and Dependent Variables
For each pair of variables, identify the independent variable and the dependent variables.
a. number of traffic violations, cost of auto insurance
SOLUTION
independent variable: number of traffic violations; dependent variable: cost of auto insurance
The cost of auto insurance depends upon the number of traffic violations.
b. electric bill total, kilowatts of electricity used
SOLUTION
independent variable: kilowatts of electricity used; dependent variable: electric bill total
Electric bills are based, or dependent, on the electricity usage. The kilowatts of electricity determine the electric bill total.
Reading Math
In an ordered pair (x, y), x is the independent variable and y is the dependent variable.
Variables
Independent variable: The variable whose value can be chosen. Also called the input variable.
Dependent variable: The variable whose value is determined by the input value of another variable. Also called the output value.
Math Reasoning
Analyze The total charge on a bill is usually a dependent variable. Explain.
Example
2
Lesson 20 111