You can go to a lot of trouble simplifying the 2-point equation for a line, or you can take a moment and simply observe that
x - y = 3 _____
(y-1)=(x-4)(2-1)/(5-4) (2-point form for the equation of a line)
y-1 = x-4 (simplified)
3 = x - y (add 4-y, swap sides to get the above standard form)
x - y = 3 _____
(y-1)=(x-4)(2-1)/(5-4) (2-point form for the equation of a line)
y-1 = x-4 (simplified)
3 = x - y (add 4-y, swap sides to get the above standard form)