The lines 2x−2=−2y=16z−7 and 4x+3=3y+2=1z+2 intersect at the point P. If the distance of P from the line 2x+1=3y−1=1z−1 is l, then 14l2 is equal to
Answer: 108
Solution
For the first line, 2x−2=−2y=16z−7=λ gives the point (2+2λ,−2λ,7+16λ).
For the second, 4x+3=3y+2=1z+2=k gives (−3+4k,−2+3k,−2+k).
Equating x and y-coordinates:
2+2λ=−3+4k,−2λ=−2+3k.
From the second, λ=22−3k. Substituting into the first: 4−3k=−3+4k⇒7k=7⇒k=1, so λ=−21.
Checking z: 7+16(−21)=−1 and −2+1=−1 — consistent. So P=(1,1,−1).
The third line passes through A(−1,1,1) with direction b=(2,3,1). Then AP=(2,0,−2).
The perpendicular distance from P to this line satisfies
l2=∣AP∣2−(∣b∣AP⋅b)2.
AP⋅b=4+0−2=2, ∣b∣2=4+9+1=14, ∣AP∣2=4+0+4=8.
l2=8−144=8−72=754.
14l2=14×754=108.
JEE Main · 2024 · 27 Jan 2024 · Shift 2 · Integer answer