The equation of a line is written as y = Mx + b where m is the slope and b is the y intercept.
Replace y and x with the given point and m with the given slope to solve for b:
-2 = -1/2(4) + b
Simplify:
-2 = -2 + b
Add 2 to both sides:
B =0
The equation becomes: y = -1/2x