Final answer:
The correct equation for a straight-line graph is based on its slope and y-intercept, expressed as y = mx + b. Determine the slope by the rise over run and find the y-intercept where the line meets the y-axis. The letters representing variables may change depending on the context, such as V for the vertical axis in a physics graph.
Step-by-step explanation:
The correct equation for a straight-line graph can be identified by its slope and y-intercept, typically expressed in the form y = mx + b, where m represents the slope and b represents the y-intercept. To determine the equation from a graph, you can find the slope by calculating the rise over run, which is the change in the y-value divided by the change in the x-value for any two points on the line. Additionally, the y-intercept is the value of y where the line crosses the y-axis. In a science context, these variables might be represented by different letters, such as V for the y-axis and t for the x-axis, where V = at + v0 with a representing the slope (acceleration) and v0 representing the initial velocity or y-intercept.
For instance, if the graph shows a line that crosses the y-axis at 9 and has a slope of 3, the equation would be y = 3x + 9. Similarly, if analyzing a graph of displacement versus time with constant velocity, the line's slope would be the velocity, and the equation might take the form y = vt, where v is the slope (constant velocity) and there is no y-intercept since the line passes through the origin.