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If a = 2i + 3j − k and b = i − j + 2k then a · b equals
A1
B5
C7
D-3
Answer & Solution
Correct answer: D. -3
1. a · b = (2)(1) + (3)(-1) + (-1)(2).
2. = 2 − 3 − 2.
3. = -3.
_Source: Maharashtra Balbharati Std XII Mathematics Part 1, Ch 5 "Vectors" §5.4_
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