Warm Up Determine whether each equation is a linear equation. If so, write the equation in standard form and determine the x-intercept and the y-intercept.

Algebra 1 Glencoe McGraw-Hill JoAnn Evans Math 8H Graphing Linear Equations in One Variable Algebra 1 Glencoe McGraw-Hill JoAnn Evans

What do each of these ordered pairs have in common? (4, -3) (4, -2) (4, -1) (4, 0) (4, 1) (4, 2) (4, 3) (4, 4) (4, 5) The x-coordinate is always the same. The y-coordinate varies. Graph each point on the same coordinate plane.

The equation that represents this relationship between x and y is x = 4. The graph of x = 4 is a VERTICAL LINE that crosses the x-axis at 4. All the points of this line (and no other points) have an x-coordinate of 4. y x Notice that the equation doesn’t have a y variable. The equation will never intersect the y-axis.

What do each of these ordered pairs have in common? (-4, -1) (-3, -1) (-2, -1) (-1, -1) (0, -1) (1, -1) (2, -1) (3, -1) (4, -1) The y-coordinate is always the same; the x-coordinate varies.

Notice that the equation doesn’t have an x variable Notice that the equation doesn’t have an x variable. The equation will never intersect the x-axis. y The equation that represents this relationship between x and y is y = -1. The graph of y = -1 is a HORIZONTAL LINE that crosses the y-axis at -1. All the points of this line (and no other points) have y- coordinate of -1. x

Sketching Horizontal and Vertical Lines Sketch the graph of x = 2. y The equation does not have y as a variable. The equation says that the x-coordinate will always be 2, regardless of the value of y. x To graph the equation, put a dot on the x-axis at 2. There is no y variable in the equation, so the equation of this line will never cross the y-axis.

Sketching Horizontal and Vertical Lines Sketch the graph of y = -3. y The equation does not have x as a variable. The equation says that the y-coordinate will always be -3, regardless of the value of x. x To graph the equation, put a dot on the y-axis at -3. There is no x variable in the equation, so the equation of this line will never cross the x-axis.

Sketch the graphs of x = 7 and y = -4 Sketch the graphs of x = 7 and y = -4. Find the point of intersection of the two graphs. y Graph x = 7. Plot a point on the x-axis at 7. The equation has no y-value, so the line will never cross the y-axis. x Graph y = -4. Plot a point on the y-axis at -4. The equation has no x-value, so the line will never cross the x-axis. (7, -4)

Sketch the graphs of x = -4 and y = -1 Sketch the graphs of x = -4 and y = -1. Find the point of intersection of the two graphs. y Graph x = -4. Plot a point on the x-axis at -4. The equation has no y-value, so the line will never cross the y-axis. x Graph y = -1. Plot a point on the y-axis at -1. The equation has no x-value, so the line will never cross the x-axis. (-4, -1)

Write equations for the horizontal line and the vertical line that pass through the point (-7, -3) Plot the point (-7, -3). Graph a vertical line through the point. The line intersects the x-axis at -7. It never intersects the y-axis. What is its equation? y x = -7 x Graph a horizontal line through the point. The line intersects the y-axis at -3. It never intersects the x-axis. What is its equation? y = -3