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If `veca, vecb and vecc` are unit vectors satisfying `|veca-vecb|^(2)+|vecb-vecc|^(2)+|vecc-veca|^(2)=9 " then " |2veca+ 5vecb+ 5vecc|` is |
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Answer» Correct Answer - 3 As `|veca-vecb|^(2)+|vecb-vecc|^(2)+|vecc-veca|^(2)` `=3(|veca|^(2)+|vecb|^(2)+|vecc|^(2))-|veca+vecb+vecc|^(2)` `Rightarrow 3xx 3-|veca+vecb+vecc|=9` `or |veca +vecb+vecc|=0` `veca +vecb +vecc=0` `or vecb +vecc=-veca` `Rightarrow |2veca+5(vecb +vecc)|=|-3veca|=3|veca|=3` |
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