10th Class Mathematics Coordinate Geometry Question Bank Coordinate Geometry

  • question_answer
    If the points (a, 0), (0. b} and (1,1) are collinear then which of the following is true?

    A)  \[\frac{1}{a}+\frac{1}{b}=2\]       

    B)  \[\frac{1}{a}-\frac{1}{b}=1\]         

    C)  \[\frac{1}{a}-\frac{1}{b}=2\]         

    D)  \[\frac{1}{a}+\frac{1}{b}-1\]

    Correct Answer: D

    Solution :

    Since, the given points A (a, 0), B(0, b) and C(1, 1) are collinear. \[\therefore \]  Area of \[\Delta ABC=0\] \[\Rightarrow \] \[\frac{1}{2}|a(b-1)+0(1-0)+1(0-b)|=0\] \[\Rightarrow \] \[ab-a-b=0\,\,\,\Rightarrow \,\,a+b=ab\] Dividing both sides by ab, we get. \[\frac{1}{b}+\frac{1}{a}=1\]  \[\Rightarrow \] \[\frac{1}{a}+\frac{1}{b}=1\]


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