diketahui persamaan garis k sejajar garis k sejajar garis 3x+7y-9=0 .Persamaan garis yang melalui titik B(6,-1) dan tegak lurus garis k adalah

m1 = -a                              m1 x m2 = -1
        ----                              -3  x m2 = -1
          b                              ----
     = - 3                               7
       -----                                     m2 = 7
          7                                             ----
                                                           3



y -y- = m (x -x1)
y- (-1) = 7 (x -6)
            ---
             3
---------------------  x 3
3y + 3 = 7 (x - 6)
3y + 3 = 7x - 42
7x - 3y -45 = 0