You could use the equation y=mx+b
Find the slope of the two coordinates. I would personally suggest using stack and subtract:
(0,2) 2-5 -3 3
(2,5) -------= ------= -----
0-2 -2 2
We have the slope but we need to find the y-intercept.
y=3
--x+b
2
Plug one of the coordinates in the constructed equation above:
2=3
-- (0)+b
2
2=0+b
-0=-0
------------
b=2
We found the slope and y-intercept. Now we have our complete equation. The equation is:
y=3
--x+2
2
Have a blessed day!