If A = 5i - 2j and B = -3i + 4j, what is the value of A · B?

Practice Questions

Q1
If A = 5i - 2j and B = -3i + 4j, what is the value of A · B?
  1. -23
  2. -7
  3. 7
  4. 23

Questions & Step-by-Step Solutions

If A = 5i - 2j and B = -3i + 4j, what is the value of A · B?
  • Step 1: Identify the components of vector A. A = 5i - 2j means A has a component of 5 in the i direction and -2 in the j direction.
  • Step 2: Identify the components of vector B. B = -3i + 4j means B has a component of -3 in the i direction and 4 in the j direction.
  • Step 3: Use the formula for the dot product A · B, which is A · B = (A's i component) * (B's i component) + (A's j component) * (B's j component).
  • Step 4: Substitute the values into the formula: A · B = (5) * (-3) + (-2) * (4).
  • Step 5: Calculate the first part: (5) * (-3) = -15.
  • Step 6: Calculate the second part: (-2) * (4) = -8.
  • Step 7: Add the results from Step 5 and Step 6: -15 + (-8) = -15 - 8.
  • Step 8: Final calculation: -15 - 8 = -23.
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