Final answer:
The slope of the line described in Figure A1 is 3, implying a consistent rise of 3 on the y-axis for each increase of 1 on the x-axis. The slope, once determined, does not change along the length of the straight line. Understanding slope is crucial in interpreting graphs and data in various fields such as algebra and physical sciences.
Step-by-step explanation:
The slope of a straight line in a graph represents the rate of change between the variables on the horizontal (x-axis) and vertical (y-axis) axes. According to Figure A1, the slope of the line crossing the y-axis at the y-intercept of 9 is stated to be 3. This indicates that for every 1 unit increase in x, there is a 3 unit increase in y, which can be summarized as a 'rise over run' of 3/1. The slope remains consistent along the entire length of a straight line, which means the rise and run ratio does not change.
The elevation of the lowest point along the line and the total relief along the line in a cross-section are obtained by reading the values directly from the graph, where the lowest point refers to the smallest y-value on the line, and the total relief is the vertical difference between the highest and lowest points on the line.