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  1. If a2 + b2 + c2 = 2 (a – b – c) – 3, then the value of 2a – 3b + 4c is
    1. 1
    2. 7
    3. 2
    4. 3
Correct Option: A

Given that :- a2 + b2 + c2 = 2 (a – b – c) – 3
⇒ a2 + b2 + c2 - 2 (a – b – c) + 3 = 0
⇒ a2 + b2 + c2 - 2a + 2b + 2c + 3 = 0
⇒ ( a2 + 1 - 2a ) + ( b2 + 1 + 2b ) + ( c2 + 1 + 2c ) = 0
⇒ ( a - 1 )2 + ( b + 1 )2 + ( c + 1 )2 = 0
This is possible when ( a - 1 )2 = 0, ( b + 1 )2 = 0, and ( c + 1 )2 = 0
⇒ a = 1, b = –1, c = –1
Thus, 2a – 3b + 4c = 2 (1) – 3 (–1) + 4 (–1)
2a – 3b + 4c = 2 + 3 – 4 = 1.



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