a perpendicular line has a slope that is the OPPOSITE and the RECIPROCAL of the original slope.
first you need the slope from this equation, and that means isolating the y.
-x + 2y = 4
2y = x + 4
y = (1/2)x + 4
so the original slope is (1/2). to find the perpendicular slope, you need to get the opposite reciprocal of the slope. the opposite, negative, and the reciprocal, 2.
your perpendicular slope is 2, then you have to make sure it passes through (-2, 1), so you'll go into point-slope
y - 1 = 2(x + 2)
y - 1 = 2x + 4
y = 2x + 5 should be your answer.
