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If → a is a non-zero vector such that its projections on the vectors 2 i ˆ − j ˆ + 2 k ˆ , i ˆ + 2 j ˆ – 2 k ˆ and k ˆ are equal, then a unit vector along → a is :

1. 155 1 (7 i ˆ +9 j ˆ + 5 k ˆ )
2. 155 1 (7 i ˆ + 9 j ˆ – 5 k ˆ )
3. 155 1 (–7 i ˆ + 9 j ˆ – 5 k ˆ )
4. 155 1 (–7 i ˆ + 9 j ˆ + 5 k ˆ )

Correct answer: 155 1 (7 i ˆ +9 j ˆ + 5 k ˆ )

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