CBSE Class 12 Math 2018 Solved Paper

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Question : 28 of 29
 
Marks: +1, -0
Find the distance of the point (-1,-5,-10) from the point of intersection of the line
r→ = 2i^−j^+2k^ + λ (3i^+4j^+2k^) and the plane r→ = (i^−j^+k^) = 5
Solution:
Equation of line is r→ = 2i^−j^+2k^ + λ (3i^+4j^+2k^)
r→ = (2 + 3λ) i^ + (- 1 + 4λ) j^ + (2 + 2λ) k^
This lies on the plane r→ = (i^−j^+k^) = 5
⇒ [(2 + 3λ) i^ + (- 1 + 4λ) j^ + (2 + 2λ) k^] . (i^−j^+k^) = 5
⇒ (2 + 3λ) + (- 1 + 4λ) (- 1) + (2 + 2λ) = 5
⇒ λ = 0
Coordinates are
(2 + 3λ , - 1 + 4λ , 2 + 2λ) = (2 , - 12)
Distance between (2 , - 1 , 2) and (- 1 , - 5 , - 10)
=
(−1−2)2+(−5−1)2+(−10−2)2

= 13 units
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