Question

If $\mathbf{a} = 3\mathbf{i} - 2\mathbf{j} + \mathbf{k},\mathbf{b} = 2\mathbf{i} - 4\mathbf{j} - 3\mathbf{k}$ and $\mathbf{c} = - \mathbf{i} + 2\mathbf{j} + 2\mathbf{k},$

then $\mathbf{a} + \mathbf{b} + \mathbf{c}$ is

• A. $3\mathbf{i} - 4\mathbf{j}$
• B. $3\mathbf{i} + 4\mathbf{j}$
• C. $4\mathbf{i} - 4\mathbf{j}$
• D. $4\mathbf{i} + 4\mathbf{j}$

Answer 1

Answer: (C)

$4\mathbf{i} - 4\mathbf{j}$

Answer 2

$\mathbf{a} + \mathbf{b} + \mathbf{c} = (3 + 2 - 1)\mathbf{i} + ( - 2 - 4 + 2)\mathbf{j} + (1 - 3 + 2)\mathbf{k}$

$= 4\mathbf{i} - 4\mathbf{j}$.