2 1.

( 1)

Let the linear equation of AC be y=kx+b, because A (0 0,4) and C (-8,0) are in a straight line, we can get.

b=4，k=0.5

So the Del linear equation of AC is: y=0.5x+4.

(2)

The abscissa x=(0-8)/2=-4 of AC midpoint d and the ordinate y=(4+0)/2=2.

Let the linear equation of BD be y=kx+b, because B (-2,6) and D (-4,2) are in a straight line, which can be brought in.

b= 10，k=2

Therefore, the linear equation of BD on the AC side is: y=2x+ 10.