Find a × b for a = 3i − 2j − 1k and b = 2i + 4j + 4k.
Answer and explanation
Correct answer: C. -4i − 14j + 16k
- Step 1: Use the determinant with rows (i, j, k), (a₁, a₂, a₃), (b₁, b₂, b₃). Step 2. Expanding gives -4i − 14j + 16k. Answer: -4i − 14j + 16k. Why not the others: 4i + 14j − 16k is what you get if you reverse the order of the cross product. -4i + 14j + 16k is what you get if you forget the minus sign on the j component. 6i − 8j − 4k is what you get if you multiply matching components.
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