1) Perpendicular lines have a reciprocal and multiplied by -1 (opposite) to the given line.
So we can say, our perpendicular line has the slope m=-1/2
2) Since it intercepts the point (4,3) we need to plug into the slope-intercept formula:
y=mx+b
3=-1/2(4)+b
3=-2+b
3+2=b
b=5
3) So that perpendicular line can be described by the function: f(x) =-1/2x +5