If a2+9b2−4c2=6ab, then the family of line ax+by+c=0 are concurrent at:
If the three lines y=m1x+c1,y=m2x+c2 and y=m3x+c3 are concurrent then show that,
m1(c2−c3)+m2(c3−c1)+m3(c1−c2)=0