Graphs of lines are perpendicular if their lsopes multiply to -1. In this case, since the slope of the line we know is 2, the slope of our line needs to be -1/2. Now we need to find the slopes of each of these choices.
2x + y = 4
y = -2x + 4
Since -2 ≠ -1/2, the answer is not A
4x - 2y = 4
Get positive y by itself
2y = 4x - 4
y = 2x - 2
Since 2 ≠ -1/2, the answer is not B
y = -2x + 8
Since -2 ≠ -1/2, the answer is not A
2x + 4y = 1
Get y by itself
4y = -2x + 1
Get y
y = -1/2x + 1
Since -1/2 = -1/2, the answer is D
