Y = 3x - 4.....the slope here is 3. A perpendicular line will have a negative reciprocal slope. To find the negative reciprocal, u flip the slope and change the sign. So we will need a slope of -1/3...see how I flipped the slope of 3/1 and made it 1/3...and then changed the sign, making it -1/3.
y = mx + b slope(m) = -1/3 (2,1)...x = 2 and y = 1 now we sub and find b, the y int 1 = -1/3(2) + b 1 = -2/3 + b 1 + 2/3 = b 3/3 + 2/3 = b 5/3 = b