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UPSC NDA Math Model Paper 4
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© examsnet.com
Question : 4
Total: 120
What is the value of λ for which the vectors
^
i
−
^
j
+
^
k
,
2
^
i
+
^
j
−
^
k
,
^
i
λ
−
^
j
+
^
k
λ
are coplanar
5
4
2
1
Validate
Solution:
Here,
^
i
−
^
j
+
^
k
,
2
^
i
+
^
j
−
^
k
,
^
i
λ
−
^
j
+
^
k
λ
are coplanar
⇒
|
1
−
1
1
2
1
−
1
λ
−
1
λ
|
=
0
⇒
1
(
λ
−
1
)
+
1
(
2
λ
+
λ
)
+
1
(
−
2
−
λ
)
=
0
⇒
3
λ
=
3
⇒ λ = 1
Hence, option (4) is correct
© examsnet.com
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