If $\vec a = 4\hat i + 3\hat k$ and $\vec b = -2\hat i + \hat j + 5\hat k$, then $2\vec a + 5\vec b$ equals:
A$-2\hat i + 5\hat j + 31\hat k$
B$18\hat i + 5\hat j + 31\hat k$
C$2\hat i + 5\hat j - 31\hat k$
D$-2\hat i + \hat j + 8\hat k$
Answer & Solution
Correct answer: A. $-2\hat i + 5\hat j + 31\hat k$
$2\vec a = 8\hat i + 6\hat k$; $5\vec b = -10\hat i + 5\hat j + 25\hat k$. Sum: $-2\hat i + 5\hat j + 31\hat k$.
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