pakai cara ya...mksh:)

18.
(y - y1) = m(x - x1)
y - (-1) = 2/3(x - 4)
3(y + 1) = 2(x - 4)
3y + 3 = 2x - 8
3y - 2x + 11 = 0

19.
Gradien = -3/1 = -3
melewati titik (-2,0)

(y - y1) = m(x - x1)
y - 0 = -3(x-(-2))
y = -3x - 6
y + 3x + 6 = 0