Final answer:
Using the provided slope of 3 and y-intercept of 9 from Figure A1, the slope-intercept form of the equation of the line is y = 3x + 9. The independent variable is x, and the dependent variable is y.
Step-by-step explanation:
The question concerns the mathematical concept of the slope-intercept form of a linear equation, which is commonly represented as y = mx + b, where m stands for the slope of the line, and b stands for the y-intercept. According to the information provided in Figure A1, the slope (m) of the line is 3, meaning that for every unit the x-value increases, the y-value increases by 3. Similarly, the y-intercept (b) of the line is 9, indicating that the line crosses the y-axis at the point (0, 9).
Therefore, using the slope-intercept form, the equation of this particular line can be written as y = 3x + 9. The independent variable in this equation is x, which represents the input or cause, while the dependent variable is y, which represents the output or effect. The y-intercept of 9 tells us where the line crosses the y-axis, and the slope of 3 explains the steepness of the line, signaling that for every increase by 1 in the x-direction, there is a corresponding increase of 3 in the y-direction.