ini caranya gmn yaaa tolong jelasin secara detail makasih:))

m1 = (Y2 - Y1)/(X2 - X1)
m1 = (-1 - 0) / ( 0 - 2)
m1 = 1/2

m1m2 = -1
1/2 m2 = -1
m2 = -2

y - Y1 = m2(x - X1)
y - 0 = -2(x - 2)
y = -2x + 4
2x + y - 4 = 0