Two of the lines represented by `ax^3+3bx^2y+3cxy^2+dy^3=0` will be perpendicular if 1) `a^2 + ac + db +d^2=0` 2) `a^2+3(ac+bd)+d^2=0` 3) `a^2-3(ac + bd)+d^2=0` 4) `a^2-ac-bd+d^2=0`