y = 2x - 3...slope here is 2. A perpendicular line has a negative reciprocal slope. All that means is flip the slope and change the sign. So our perpendicular line will have a slope of -1/2 (see how I flipped 2/1 and made it 1/2...I then changed the sign, making it -1/2)
y = mx + b
slope(m) = -1/2
(1,2)...x = 1 and y = 2
now we sub and find b, the y int
2 = -1/2(1) + b
2 = -1/2 + b
2 + 1/2 = b
4/2 + 1/2 = b
5/2 = b
so ur perpendicular equation is : y = -1/2x + 5/2
