Answer:
y = -2x + 16.
Explanation:
The slope of the perpendicular line = -1 / slope of the given line
= -1 / 1/2 = -2.
Using the point slope form of the equation of a straight line:
y - y1 = m (x - x1)
y - 8 = -2(x - 4)
y - 8 = -2x + 8
y = -2x + 16 is the required equation.