perpendicular means the two lines' slopes are negative reciprocal to each other. the slope of the given line is 1/3, therefore the slope of the perpendicular line is -3/1, which is -3
use the point-slope form: the given point is (4,1), so (y-1)=-3(x-4)
you can stop right here or you can write it into slope intercept form:
y-1=-3x+12
y=-3x+13
