tolong!! bantu yang baik☺ yang no 5

mis : C = (x,y,z)
AC : CB = 1 : 3
(x-5) : (9-x) = 1 : 3
3(x-5) = 1(9-x)
3x - 15 = 9 - x
3x + x = 9 + 15
4x = 24
x = 24/4 = 6

(y-2) : (10-y) = 1 : 3
3(y-2) = 1(10-y)
3y - 6 = 10 - y
3y + y = 10 + 6
4y = 16
y = 16/4 = 4

(z-1) : (13-z) = 1 : 3
3(z-1) = 1(13-z)
3z - 3 = 13 - z
3z + z = 13 + 3
4z = 16
z = 16/4 = 4

Jadi C (6,4,4)
Vektor u = AC
= (1,2,3)
Vektor v = CB
= (3,6,9)

B.
u.v = (1.3 + 2.6 + 3.9)
= (3 + 12 + 27)
= 42