Let the lines L1:r=i^+2j^+3k^+λ(2i^+3j^+4k^), λ∈R and L2:r=(4i^+j^)+μ(5i^+2j^+k^),μ∈R, intersect at the point R . Let P and Q be the points lying on lines L1 and L2, respectively, such that ∣PR∣=29 and ∣PQ∣=347. If the point P lies in the first octant, then 27(QR)2 is equal to
A
Option A:
340
B
Option B:
360
Correct
C
Option C:
320
D
Option D:
348
Answer: B
Step-by-step solution
For POI 2λ+1=5μ+4;3λ+2=2μ+1;4λ+3=μ
⇒λ=μ=−1
R(−1,−1,−1)P(2λ+1,3λ+2,4λ+3)
PR2=29⇒(2λ+2)2+(3λ+3)2+(4λ+4)2=29
⇒λ=0 or λ=−2 (Reject)
⇒P(1,2,3)
Q(5μ+4,2μ+1,μ)
∣PQ∣=347⇒PQ2=347
⇒(5μ+3)2+(2μ−1)2+(μ−3)2=347
⇒μ=−31
Q=(37,31,−31)
(QR)2=(37+1)2+(31+1)2+(−31+1)2
=9100+16+4=9120
⇒27×(QR)2=27×9120=360
Answer key and solution verified before publishing.
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