Find a × b for a = 3i + 0j + 4k and b = 3i + 4j − 2k.
Answer and explanation
Correct answer: A. -16i + 18j + 12k
- Step 1: Use the determinant with rows (i, j, k), (a₁, a₂, a₃), (b₁, b₂, b₃). Step 2. Expanding gives -16i + 18j + 12k. Answer: -16i + 18j + 12k. Why not the others: 16i − 18j − 12k is what you get if you reverse the order of the cross product. -16i − 18j + 12k is what you get if you forget the minus sign on the j component. 9i + 0j − 8k is what you get if you multiply matching components.
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