Question

Let $\vec{a}\times(2\hat{i}+3\hat{j}+4\hat{k})=(2\hat{i}+3\hat{j}+4\hat{k})\times\vec{b}$. If $|\vec{a}+\vec{b}|=\sqrt{29}$, then $\vec{a}+\vec{b} = $ ________.

• A. $(2\hat{i}+3\hat{j}-4\hat{k})$
• B. $-(2\hat{i}+3\hat{j}-4\hat{k})$
• C. $\pm(2\hat{i}+3\hat{j}+4\hat{k})$
• D. $\pm(2\hat{i}-3\hat{j}+4\hat{k})$
• E. $\pm\sqrt{29}(2\hat{i}+3\hat{j}+4\hat{k})$

Hint:

$\vec{A} \times \vec{B} = 0 \iff \vec{A}$ is parallel to $\vec{B}$.

Answer 1

The Correct Option is C