Hi Shirley, to answer this question, start by finding the slope represented by the two points.
Slope = (y2 - y1) / (x2 - x1)
It does not matter which point is used for (x1, y1) or (x2, y2)
Let (5, 2) be the (x2, y2) point and (4, 1) be the (x1, y1)
Slope = (2 - 1) / (5 - 4)
Slope = 1 / 1 or 1
Next, find the point-slope form of the line using the slope, m, and one of the two given points and again, it does not matter which point is selected.
y - y1 = m * (x - x1)
m = 1
y1 = 2
x1 = 5
y - 2 = 1 * (x - 5)
y - 2 = x - 5
You now have the point slope format of the line.
Add 2 to both sides:
y = x - 3
You now have the slope-intercept form of the line.