To find the equation of a line, you can start by finding the slope. Use the two given points to find the slope. The slope is the ratio of the change in y-values over the change in x-values.
The two points are (4, 1) and (5, 2), so the change in y-values is 2-1 = 1. The change in x-values is 5-4 = 1. So, the ratio is 1/1. The slope for this line is 1.
Now that you know the slope, you need to find the y-intercept (this is one way to proceed).
The slope-intercept form of all linear equations is y=mx+b. The m is the slope, which we already know is 1.
So we know:
y=1x+b
Temporarily plug in one of the two points for x and y. I will use (4, 1).
1=1(4) +b
1= 4 + b
-3 = b
So, now you know the slope-intercept equation is y=x+-3
You need to change this into Standard Form: Ax + By = C (A, B, C need to be integers. A should be positive).
y = x + -3
y - x = -3
-x + y = -3
x + -y = 3
(That last step is to be sure that the A value is positive.)