10x-20y+5 tentukan gradien dr garis tegak lurus

10x – 20y + 5 = 0
20 y = 10x + 5
y = 1/2 x + 1/4

m1 = 1/2

tegak lurus, berarti
m1 x m2 = -1
1/2 x m2 = -1
m2 = -2