You can put this solution on YOUR website! A line with an undefined slope is a vertical line, i.e. parallel to the y-axis. All of the points on a vertical line passing through the point (-8,0) must have an x coordinate of -8, so the equation x = -8 completely describes this line.
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The slope of a line given any two points on the line is given by , but for the line x = -8, the x coordinates of any two points on the line are equal, namely -8. Therefore, the denominator of the expression for the slope is zero, so the slope is undefined.
