As we go from (-1,4) to (3,0), increases by 4 and y decreases by 4. Thus, the slope of this line is m = rise / run = -4/4 = -1.
Let's use the slope-intercept form of the equation of a line:
y = mx + b
Replace y with 0 and x with 3 (from (3,0), and m with -1:
0 = (-1)(3) + b. Then b = 3, and the desired equation is y = -x + 3.
