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Question : 19 of 120
Marks:
+1,
-0
Solution:
Given a⟂b
⇒a⋅b=0
=a×{a×{a×(a×b)}}
=a×{a×{(a⋅b)a−(a⋅a)b}}
=a×{a×{0−(a⋅a)b}}
=a×{−(a⋅a)(a×b)}
=a×{(a⋅a)(b×a)}
=(a⋅a){a×(b×a)}
=(a⋅a){(a⋅a)b−(a⋅b)a}
=(a⋅a){(a⋅a)b−0}
=(a⋅a)2b     (∵(a⋅a)=|a|2)
=(|a|2)2b
‌=|a|4b
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