If (a b)^2 + (a , ,. , ,b)^2 = 144 and |a| , = 4, then |b| , = - Vidyadip

MCQ

If ${(a \times b)^2} + {(a\,\,.\,\,b)^2} = 144$ and $|a|\, = 4,$ then $|b|\, = $

A
$16$
B
$8$
✓
$3$
D
$12$

✓

Answer

Correct option: C.

$3$

c
(c) We know that ${(a \times b)^2} + {(a\,.\,b)^2} = \,|a{|^2}|b{|^2}$

$\therefore \,\,\,144 = 16|b{|^2} \Rightarrow \,|b| = 3.$

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