If A = 4i + 3j and B = ai + bj, and A · B = 24, find the value of a + b if a = 2

Practice Questions

Q1
If A = 4i + 3j and B = ai + bj, and A · B = 24, find the value of a + b if a = 2.
  1. 10
  2. 12
  3. 8
  4. 6

Questions & Step-by-Step Solutions

If A = 4i + 3j and B = ai + bj, and A · B = 24, find the value of a + b if a = 2.
  • Step 1: Identify the vectors A and B. A = 4i + 3j and B = ai + bj.
  • Step 2: Substitute the value of a into vector B. Since a = 2, B becomes 2i + bj.
  • Step 3: Calculate the dot product A · B. The formula for the dot product is A · B = (4)(2) + (3)(b).
  • Step 4: Simplify the dot product calculation. This gives us A · B = 8 + 3b.
  • Step 5: Set the dot product equal to 24, as given in the question. So, 8 + 3b = 24.
  • Step 6: Solve for b. Subtract 8 from both sides: 3b = 24 - 8, which simplifies to 3b = 16.
  • Step 7: Divide both sides by 3 to find b. So, b = 16 / 3.
  • Step 8: Now, find the value of a + b. Since a = 2 and b = 16/3, we calculate a + b = 2 + 16/3.
  • Step 9: Convert 2 into a fraction with a denominator of 3. This gives us 2 = 6/3.
  • Step 10: Add the fractions: 6/3 + 16/3 = (6 + 16) / 3 = 22 / 3.
  • Step 11: The final answer for a + b is 22 / 3.
  • Dot Product – Understanding the dot product of two vectors and how to calculate it using their components.
  • Algebraic Manipulation – Solving equations for unknown variables and performing arithmetic operations.
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