Alright, so since the slope of the perpendicular line is -1/(slope), we get (-1/2)=-1/2 and y=(-1/2)x + something. Plugging 7 in as y and -4 in as x, we get 7=(-1/2)(4)+something (let's make it a variable b), and multiplying it out we get 7=-2+b. Adding 2 to both sides, we get 7+2=9=b, so the perpendicular line equation is therefore y=(-1/2)x+b
