Dua buah garis 3x-6y+12=0 dan 4y+Ax-2=0.agar ledia garis saling tegak lurus,maka nilai A adalah a.-2 b.-8 c.8 d.2

3x - 6y + 12 = 0
- 6y = - 3x - 12
m = - 3/-6
m = ½

gradien saling tegak lurus
m1 . m2 = - 1
½ . m2 = - 1
m2 = - 2

garis
4y + ax - 2 = 0
4y = - ax + 2
m = - a/4
- 2 = - a / 4
- 2 ( 4) = - a
- 8 = - a
a = 8 ( C )