So parallel lines have the same slope, but perpendicular lines have negative reciprocal slopes. So a slope of 3/2 will have a negative reciprocal of -2/3.
-x + 2y = 4
2y = x + 4
2y/2 = (x + 4)/2
y = 1/2 x + 2
m = 1/2, so reciprocal is -2/1 = -2
point (-2, 1)
point-slope form:
y-y1 = m (x-x1)
y-1 = -2 (x- -2)
y-1 = -2 (x+2)
y-1 = -2x -4
y = -2x - 3, or:
2x + y = -3
