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Let vecu,vecv and vecw be vectors such t...

Let `vecu,vecv and vecw` be vectors such that `vecu+ vecv + vecw =0` if `|vecu|= 1, |vecv|=2 and |vecw|=3` then `vecu.vecv + vecv .vecw + vecw .vecu ` is

A

7

B

`-25`

C

0

D

-7

Text Solution

Verified by Experts

The correct Answer is:
b
since `vecu + vecv+vecw=0`, we have
`|vecu + vecv + vecw|^(2) =0`
`or |vecu|^(2)+|vecv|^(2)+|vecw|^(2)+2(vecu.vecv+vecv.vecw+vecw.vecu)`
`or 9 +16+25+2(vecu.vecv +vecv.vecw+vecw.vecu)=0`
`or vecu.vecv + vecv.vecw + vecw.vecu = -25`
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