Question

(a + b)•(a + b)= 1 a 12 + 1612.
(NCERT)
26. If the coordinates of four points are A (2, 3, 4), B (5, 4, -1), C (3, 6, 2) and D (1, 2, 0), then
show that AB is perpendicular to CD
(NCERT Exemplar)​

Answer 1

26
Drs of AB are (3,1,-5)
Drs of CD are (-2,-4,-2)
Therefore- 6-4+10 is =0
perpendicular