tolong dong kak nomer 30,31 sama caranya

30. ?
31. 
Diketahui : -m : 2, (-4,3) : x1 = -4, y1= 3
Ditanya : Pers. Garis?
Jawab:
y-y1 = m(x-x1)
y-3 = 2(x-(-4))
y-3 = 2(x+4)
y-3 = 2x+8
y = 2x+8+3
y = 2x + 11
2x-y-11 = 0

*Seharusnya jawabannya : 2x+y-11 = 0