The slope is 3, and the y-intercept is 9 in the provided Figure A1 Slope and the Algebra of Straight Lines.
The slope of a line on a graph indicates its steepness, and the value is calculated as the rise over the run. The y-intercept is the point where the line crosses the y-axis, represented as (0, a) in the slope-intercept form y = a + bx. Based on the provided information for Figure A1 Slope and the Algebra of Straight Lines, the slope of the line is 3 because there is a rise of 3 on the vertical axis for every 1 unit increase on the horizontal axis. Furthermore, the y-intercept is 9, which is the y-coordinate where the line intersects the y-axis.