10th Class Mathematics Coordinate Geometry Question Bank MCQs - Coordinate Geometry

  • question_answer
    The fourth vertex D of a parallelogram \[ABCD\] whose there vertices are \[A(-2,3),\] \[B(6,7)\] and \[C(8,3)\] is (NCERT EXEMPR)

    A) \[(0,1)\]

    B) \[(0,-1)\]

    C) \[(-1,0)\]

    D) \[(1,0)\]

    Correct Answer: B

    Solution :

    [b] Let the fourth vertex of parallelogram be \[D({{x}_{4}},{{y}_{4}})\] and LM the mid-points of AC and BD, respectively.
    \[\therefore \,\,\,\,\,\,\,\,L=\left( \frac{-2+8}{2},\frac{3+3}{2} \right)=\,(3,3)\]
    and \[M=\left( \frac{{{x}_{4}}+6}{2},\frac{{{y}_{4}}+7}{2} \right)\]
    Since, ABCD is a parallelogram, therefore diagonals AC and BD will bisect each other.
    Hence, L and M are the same points.
    \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\frac{{{x}_{4}}+6}{2}=3\] and \[\frac{{{y}_{4}}+7}{2}=3\]
    \[\Rightarrow \,\,\,\,\,\,\,{{x}_{4}}+6=6\] and \[{{y}_{4}}+7=6\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{x}_{4}}=0\] and \[{{y}_{4}}=6-7\]
    \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{x}_{4}}=0\] and \[{{y}_{4}}=-1\]
    Hence, the fourth vertex of parallelogram is \[D(0,-1)\].


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