Question 576480
The solution to this problem is quite simple :

First,to find the gradient of the line you divide -1 by -3 because the product of the gradient of perpendicular lines is -1.Therefore the gradient of the perpendicular line is 3.

Now just substitute the points (6,-2) into the equation y =3x+ c

You'll get -2 = 3(6)+c
           -2 =18+c
           -2-18=c
            c=-20
therefore eqn. of line perpendicular to y =-3x+4 is y =3x-20