Write the equation of the line that passes through the point (5, 4) and is perpendicular to y=2x-4

I know the opposite negative recirocal is -1/2

therefore m = -1/2
I put it in point slope form and came up with
y-4=-1/2(x-5)
I distributed it and got
y-4= -1/2x+ 2.5
but its wrong!! PLEASE HELP!!