You are given the points in which the line intercepts. Using this info, we can use these numbers to find the slope.
m = (y2-y1)/(x2-x11) = (2-4)/(2-1) = -2/1 = -2
Our end result we want is the point-slope intercept formula : y=mx+b
We are still missing b, the intercept, so pick either of the two points (it doesn't matter which) and plug them into the equation. I will use (1,4), but again you could use either.
4 = (-2)*1 + b
6 = b
So now your final equation for the line after plugging in b and m is
y = (-2)x +6
