Lesson 1-3

Example 1
Graph 4x + 3y - 5 = 0 using x- and y-intercepts.

Substitute 0 for y to find the x-intercept.  Then substitute 0 for x to find the y-intercept.

x-intercept	y-intercept		
			
The line crosses the x-axis at , and the y-axis at
. Graph the intercepts and draw the line.		

Example 2
ENTERTAINMENT  The number of U.S. commercial radio stations that play primarily top 40 music has increased from 318 in 1995 to 474 in 2002.  What was the average rate of increase in the number of top 40 radio stations?

The average rate of change is the slope of	
the line containing the points at
(1995, 318) and (2000, 474). Find the slope of the line.
m	= 
	= 	
	=  or about 22.29

On average, the number of top 40 radio stations
increased by about 22 stations per year from 1995
to 2002.

Example 3
Graph each equation using the y-intercept and the slope.

a.	y = -x - 1
The y-intercept is -1.  Graph (0, -1).
Use the slope to graph a second point.
Connect the points to graph the line.	

b.	2x - 5y = 10
Rewrite the equation in slope-intercept form.

The y-intercept is -2. Graph (0, -2). Then use the slope to graph a second point.  Connect the points to graph the line.	

Example 4
Find the zero of each function.  Then graph the function.

a.	f(x) = 2x - 3
To find the zeros of f(x), set f(x) equal to 0 and solve for x.

 is a zero of the function. So the coordinates of one point on the graph are . Find the coordinates of a second point. When x = 0, 
f(x) = 2(0) - 3, or -3. Thus, the coordinates of a second point are (0, -3).

b.	f(x) = 1
Since m = 0 and b = 1, this function has no 
x-intercept, and therefore no zeros. The graph of the function is a horizontal line 1 unit above the x-axis.