MCQ
The points (5, –4, 2), (4, –3, 1), (7, 6, 4) and (8, –7, 5) are the vertices of
  • A
    A rectangle.
  • B
    A square.
  • C
    A parallelogram.
  • None of these

Answer

Correct option: D.
None of these
Suppose:
A(5, -4, 2)
B(4, -3, 1)
C(7, 6, 4)
D(8, -7, 5)
$\text{AB}=\sqrt{(4 − 5)^2 + (−3 + 4)^2 + (1 − 2)^2}$
$=\sqrt{(−1)^2 + (1)^2 + (−1)^2}$
$=\sqrt{1 + 1 + 1}=\sqrt{3}$
$\text{BC}=\sqrt{(7 − 4)^2 + (6 + 3)^2 + (4 − 1)^2}$
$=\sqrt{(3)^2 + (9)^2 + (3)^2}$
$=\sqrt{9 + 81 + 9}=\sqrt{99}=3\sqrt{11}$
$\text{CD}=\sqrt{(8 − 7)^2 + (−7 − 6)^2 + (5 − 4)^2}$
$=\sqrt{(1)^2 + (-13)^2 + (1)^2}$
$=\sqrt{1 + 169 + 1}=\sqrt{171}$
$\text{DA}=\sqrt{(8 − 5)^2 + (−7 + 4)^2 + (5 − 2)^2}$
$=\sqrt{(3)^2 + (-3)^2 + (3)^2}$
$=\sqrt{9 + 9 + 9}=\sqrt{27}=3\sqrt{3}$
We see that none of the sides are equal.

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