First, find the slope of the line thru these 2 pts:
5-4
m = --------- = -1/2
2 -4
Use the slope-intercept formula y = mx + b:
5 = (-1/2)(2) + b. Then the y-intercept is 5 + 1, or 6: y = (-1/2)x + 6
Multiplying this entire result (3 terms) by 2 results in 2y = -x + 12, or
x + 2y = 12 (answer)