Find a × b for a = -3i + 4j + 2k and b = 3i + 1j + 2k.
Answer and explanation
Correct answer: B. 6i + 12j − 15k
- Step 1: Use the determinant with rows (i, j, k), (a₁, a₂, a₃), (b₁, b₂, b₃). Step 2. Expanding gives 6i + 12j − 15k. Answer: 6i + 12j − 15k. Why not the others: -6i − 12j + 15k is what you get if you reverse the order of the cross product. 6i − 12j − 15k is what you get if you forget the minus sign on the j component. -9i + 4j + 4k is what you get if you multiply matching components.
Practise more Algebra, calculus and vectors.
Free questions with an explanation for every one, and full timed JEE Advanced mock tests.
More Algebra, calculus and vectors questions
- What are the eigenvalues of the matrix with rows (6, 2) and (0, 2)?
- The curve has two stationary points. Find the difference between their -coordinates (larger minus smaller).
- If and are the roots of , find .
- If and , find the real part of .
- Find for and .
- Two independent events have probabilities 0.5 and 0.4. What is the probability that at least one occurs?