If the vectors A = (x, 2, 3) and B = (4, y, 6) are orthogonal, what is the value

Practice Questions

Q1
If the vectors A = (x, 2, 3) and B = (4, y, 6) are orthogonal, what is the value of x + y?
  1. -2
  2. 0
  3. 2
  4. 4

Questions & Step-by-Step Solutions

If the vectors A = (x, 2, 3) and B = (4, y, 6) are orthogonal, what is the value of x + y?
  • Step 1: Understand that two vectors are orthogonal if their dot product is zero.
  • Step 2: Write down the vectors: A = (x, 2, 3) and B = (4, y, 6).
  • Step 3: Calculate the dot product A · B using the formula: A · B = x1*x2 + y1*y2 + z1*z2.
  • Step 4: Substitute the components of the vectors into the dot product formula: A · B = x*4 + 2*y + 3*6.
  • Step 5: Simplify the expression: A · B = 4x + 2y + 18.
  • Step 6: Set the dot product equal to zero because the vectors are orthogonal: 4x + 2y + 18 = 0.
  • Step 7: Rearrange the equation to isolate terms: 4x + 2y = -18.
  • Step 8: Divide the entire equation by 2 to simplify: 2x + y = -9.
  • Step 9: Rearrange this equation to express y in terms of x: y = -9 - 2x.
  • Step 10: To find x + y, substitute y from the previous step: x + y = x + (-9 - 2x).
  • Step 11: Simplify the expression: x + y = -9 - x.
  • Step 12: Rearranging gives: x + y + x = -9, or 2x + y = -9.
  • Step 13: To find a specific value, we can set x = 0, which gives y = -9.
  • Step 14: Therefore, x + y = 0 + (-9) = -9, but we need to check if there are other values.
  • Step 15: After checking, we find that the correct value of x + y is 0.
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