A perpendicular line has a slope that is the negative reciprocal of the original line. So the product must be -1. what number * 2 =-1? Let's make this an equation: 2n= -1 (n equals the new slope of the perp. line) and solve for n. Divide both sides by 2 and you get n= -1/2. Now, you have to come up with the y-int. You may pick whatever you want. Let's just say for example: y= -1/2 x + 1. Otherwise, keeping the slope -1/2, you can pick whatever y-int you want.
