Question:

If the position vectors of the points \(A,B,C,D\) are \[ 7\hat{i}-4\hat{j}+7\hat{k},\quad \hat{i}-6\hat{j}+10\hat{k},\quad -\hat{i}-3\hat{j}+4\hat{k},\quad 5\hat{i}-\hat{j}+5\hat{k} \] respectively, then \(ABCD\) is

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To check whether four points form a parallelogram, compare opposite side vectors. If \[ \overrightarrow{AB}=\overrightarrow{DC} \] and \[ \overrightarrow{BC}=\overrightarrow{AD}, \] then the quadrilateral is a parallelogram.
Updated On: Jun 24, 2026
  • a parallelogram but not rhombus
  • a square
  • a quadrilateral which is not a parallelogram
  • a rectangle
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The Correct Option is C

Solution and Explanation

Step 1: Write the position vectors.
\[ A=(7,-4,7),\quad B=(1,-6,10) \] \[ C=(-1,-3,4),\quad D=(5,-1,5) \]

Step 2: Find the side vectors.
\[ \overrightarrow{AB}=B-A \] \[ \overrightarrow{AB}=(1-7,-6+4,10-7) \] \[ \overrightarrow{AB}=(-6,-2,3) \] Also, \[ \overrightarrow{DC}=C-D \] \[ \overrightarrow{DC}=(-1-5,-3+1,4-5) \] \[ \overrightarrow{DC}=(-6,-2,-1) \]

Step 3: Check whether opposite sides are equal.
For \(ABCD\) to be a parallelogram, \[ \overrightarrow{AB}=\overrightarrow{DC} \] But, \[ \overrightarrow{AB}=(-6,-2,3) \] and \[ \overrightarrow{DC}=(-6,-2,-1) \] These are not equal.
Therefore, \(ABCD\) is not a parallelogram.

Step 4: Final conclusion.
Hence, \(ABCD\) is \[ \boxed{\text{a quadrilateral which is not a parallelogram}} \]
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