the cartesian equations of sides BC,CA and AB of a triangel are repectively ur =a_rx+b_ry+c_r=0 ,r=1,2,3. show that the equation of the straight line passing through A and bisecting side BC is

u₃ / a₃b₁-a₁b₃ = u₂/a₁b₂-a₂b₁.