Published by:
CGP EDU Academic Team
Published on: August 14, 2026
The vector x 
+ 3 
+ 
is rotated through an angle α and twice in magnitude then it becomes (4x + 2) 
+ 2 
+ 4 
then the value of x equals-
A
– 
B
–2
C
D
2
Text Solution
Verified by ExpertsThe correct answer is:
CHECK THE SOLUTION.
(b, c)
= x 
+ 3 
+ 
and 
= (4x + 2) 
+ 2 
+ 4 
Now 2 | 
| = | 
|
⇒ 2 
= 
⇒ 4(x 2 + 10) = (4x + 2) 2 + 20 ⇒ x 2 + 10 = 4x 2 + 1 + 4x + 5 ⇒ 3x 2 + 4x – 4 = 0 ⇒ 3x (x + 2) – 2(x + 2) = 0
⇒ 3(x +2) (x – 2/3) = 0 ⇒ x = –2, 2/3
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