Find a × b for a = 2i + 0j + 2k and b = -3i − 1j − 2k.
Answer and explanation
Correct answer: C. 2i − 2j − 2k
- Step 1: Use the determinant with rows (i, j, k), (a₁, a₂, a₃), (b₁, b₂, b₃). Step 2. Expanding gives 2i − 2j − 2k. Answer: 2i − 2j − 2k. Why not the others: -2i + 2j + 2k is what you get if you reverse the order of the cross product. 2i + 2j − 2k is what you get if you forget the minus sign on the j component. -6i + 0j − 4k is what you get if you multiply matching components.
Practise more Calculus, Algebra and Trigonometry.
Free questions with an explanation for every one, and full timed ECAT Pakistan mock tests.