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3-1.Vectors
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બે સદિશો $ \overrightarrow P = a\hat i + a\hat j + 3\hat k $ અને $ \overrightarrow Q = a\hat i - 2\hat j - \hat k $ એકબીજાને લંબ હોય,તો $a =$ _________
A
$3$
B
$4$
C
$9$
D
$13$
(AIIMS-2002)
Solution
(a) $\bar P.\bar Q = 0$
$⇒$ ${a^2} – 2a – 3 = 0$ $⇒$ $a = 3$
Standard 11
Physics