Question

If the vectors 3î – 5ỹ + k and 9 î – 15j + pk are collinear,
then the value of p is ... ... ....
(a) 4
(b) -4
(c)3
(d) -3
​

Answer 1

Answer:

3

Step-by-step explanation:

If given vectors are collinear, area of parallelogram made by them should be 0. It means, their vector product is 0.

=> (3i - 5j + k) x (9i - 15j + pk) = 0

=> (-45ij + 3pik) + (-45ji - 5pjk) + (9ki - 15kj) = 0

=> -45(1) + 3p(1) - 45(-1) - 5p(1) + 9(-1) - 15(-1) = 0

=> -45 + 3p + 45 - 5p - 9 + 15 = 0

=> -2p + 6 = 0

=> p = 3

Using:

i² = j² = k² = 0

ij = ik = jk = 1

ji = ki = kj = - 1

Answer 2

Answer:-) options (C) is correct✔️

hope it is help you✍️✍️