Given : A(5,0), B(7,-4), C(5,-8), AB and BC, mPAB = ½,
mPBC = -½, midpoint of AB = (6,-2), midpoint of BC = (6,-6).
(1) Find standard form equation of line perpendicular to AB through the midpoint
(2) Find standard form equation of line perpendicular to BC through the midpoint
