Parallel Lines are lines that never intersect. Two nonvertical lines are parallel if and only if they have the same slope.

Determine if y = 2x+5 and -2x+y = -2 are parallel then graph the equations to check.

Since the slopes are the same, the two lines are parallel.

Try graphing both equations. Go to the Graph-It applet below. To graph y = 2x+5 and -2x+y = -2

Click on Set Graph Set Range to -10, 10 Set Grid Lines to 1 Type in 2 * x+5 for eq. 1 Put a Check in the box next to the function In the next box type in 2 * x-2 for eq. 2 Put a Check in the box next to the function Note: * must be used when multiplying

Determine if y = x+1 and 2x+y = 3 are parallel then graph the equations to check.

Since the slopes are the different, the two lines are not parallel.

Try graphing both equations. Go to the Graph-It applet below. To graph y = x+1 and 2x+y = 3

Click on Set Graph Set Range to -10, 10 Set Grid Lines to 1 Type in x+1 for eq. 1 Put a Check in the box next to the function In the next box type in -2 * x+3 for eq. 2 Put a Check in the box next to the function Note: * must be used when multiplying

Quick Hints:

• X is the default domain variable.
• Point to the graph to get exact values.