Final answer:
To write the equation of a line in slope-intercept form, we need to find the slope and the y-intercept. In this case, since the y-coordinates of the two points are the same, the slope is 0. The equation of the line is y = 18.
Step-by-step explanation:
To write the equation of a line in slope-intercept form, we need to find the slope and the y-intercept. The slope between two points is found by taking the difference in y-coordinates divided by the difference in x-coordinates. In this case, the two points are (4,18) and (9,18), and since the y-coordinates are the same, the slope is 0. The y-intercept is the point where the line crosses the y-axis, which can be found using either of the given points. Let's use (4,18) as the y-intercept. The equation of a line in slope-intercept form is y = mx + b, where m is the slope and b is the y-intercept. Plugging in the values, we get y = 0x + 18, which simplifies to y = 18. Therefore, the equation of the line is y = 18.