Final answer:
The slope-intercept form of a linear equation is y = 3x + 9.
Step-by-step explanation:
The slope-intercept form of a linear equation is y = mx + b, where m represents the slope of the line, and b represents the y-intercept.
The slope, m, is defined as the rise divided by the run, which means it represents how much the y value changes for every unit of change in the x value.
The y-intercept, b, is the y-coordinate of the point where the line crosses the y-axis, usually when x = 0.
An example given illustrates that a line graph with a y-intercept of 9 and a slope of 3 would have an equation of y = 3x + 9.
Here, the line rises 3 units for every 1 unit it moves along the horizontal axis, and it crosses the y-axis at the point (0, 9).