Final answer:
The line x+2=0 is a vertical line with an x-intercept at x=-2, has no y-intercept, and its slope is undefined. In comparison, a line with known slope and y-intercept, like the one in Figure A1 with a slope of 3 and y-intercept of 9, can be represented in slope-intercept form.
Step-by-step explanation:
The line x+2=0 is a vertical line. Its intercept would be at x=-2 since this is the value of x where the line crosses the x-axis. It does not have a y-intercept because a vertical line does not cross the y-axis, it runs parallel to it. The slope of this line is undefined because a vertical line has an infinite slope; it rises without running. Therefore, the slope of this line cannot be calculated in the rise over run manner, which is the typical way slope is found for non-vertical lines.
In contrast, referring to Figure A1, a line graph with x on the horizontal axis and y on the vertical axis showing a y-intercept of 9 and a slope of 3 represents a typical non-vertical line where these values can be determined. The slope indicates a rise of 3 on the vertical axis for every increase of 1 on the horizontal axis, and this is consistent along the entire length of the line. The slope-intercept form of the equation of a straight line, y = mx + b, uses m for slope and b for the y-intercept to determine the shape and position of the line on a graph.