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Horizontal and Vertical Lines

Equations of horizontal and vertical lines only have one variable . The equation x = 4 represents a vertical line which crosses the x -axis at the point ( 4 , 0 ) . Every ordered pair with 4 as its first coordinate is a solution . (The equation means “ x is equal to 4 , and y can be whatever it wants.”)

Similarly, the equation

y = 3

is a horizontal line which crosses the y -axis at ( 0 , 3 ) .

The point where the horizontal and vertical lines intersect is also easy to find.