$\begin{array}{1 1} a) 4x+2y+6=0 \;and\;12x-6y+7=0 \\ b)4x+2y+6=0 \;and\;12x+6y+18=0 \\ c)4x+2y-6=0 \;and\;-12x-6y+18=0 \\ d)-4x+2y+6=0 \;and\;12x+6y+7=0 \end{array} $
