10th Class Mathematics Pair of Linear Equations in Two Variables Question Bank MCQs - Pair of Linear Equations in Two Variables

  • question_answer
    If the lines given by \[2x+ky=1\] and \[3x-5y=7\] has unique solution, then the value of k is

    A) \[-10/3\]

    B) \[-5/3\]

    C) \[2/3\]

    D) for all real value except\[\frac{-10}{3}\]

    Correct Answer: D

    Solution :

    The given equations can be rewritten as \[2x+ky-1=0\] and\[3x-5y-7=0\].
    On comparing with \[{{a}_{1}}x+{{b}_{1}}y+{{c}_{1}}=0\]and
    \[{{a}_{2}}x+{{b}_{2}}y+{{c}_{2}}=0\], we get
    \[{{a}_{1}}=2,\,{{b}_{1}}=k,\,{{c}_{1}}=-1\]and
    \[{{a}_{2}}=3,\,{{b}_{2}}=-5,\,{{c}_{2}}=-7\]
    For unique solution,
    \[\frac{{{a}_{1}}}{{{a}_{2}}}\ne \frac{{{b}_{1}}}{{{b}_{2}}}\Rightarrow \frac{2}{3}\ne \frac{k}{-5}\Rightarrow k\ne \frac{-10}{3}\]
    Thus, given lines have a unique solution for all real values of k, except \[\frac{-10}{3}\].


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