diketahui titik p(-1,4,-1), q(4,3,-6) r(2,1,-4), nilai dari pq.qr adalah

p (-1,4,-1)
q(4,3,-6)
r(2,1,-4)

pq = q - p
= (4,3,-6) - (-1,4,-1)
= (5,-1,-5)

qr = r - q
= (2,1,-4) - (4,3,-6)
= (-2,-2,2)

pq.qr = (5,-1,-5).(-2,-2,2)
= -10 + 2 -10
= -18

maaf kalau salah

Mapel : Matematika
Kelas : X SMA
Bab : Vektor

Pembahasan :
PQ = Q - P
PQ = [4 3 -6] - [-1 4 -1]
PQ = [5 -1 -5]

QR = r - q
QR = [2 1 -4] - [4 3 -6]
QR = [-2 -2 2]

Maka...
PQ . QR
= [5 -1 -5] . [-2 -2 2]
= 5.(-2) + (-1)(-2) + (-5)(2)
= -10 + 2 - 10
= -18