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

  • question_answer
    For what value of c does the pair of equations or \[cx-y=3\]and \[\text{6x}-\text{2y}=\text{4}\] have infinitely many solutions?

    A) \[c=3\]

    B) \[c=-3\]

    C) \[c=-12\]

    D) not possible for any value of c

    Correct Answer: D

    Solution :

    [d] The given pair of equations is
    \[cx-y-3=0\] and \[6x-2y-4=0\]
    For infinitely many solutions, \[\frac{{{a}_{1}}}{{{a}_{2}}}=\frac{{{b}_{1}}}{{{b}_{2}}}=\frac{{{c}_{1}}}{{{c}_{2}}}.\]
    Here, \[\frac{{{a}_{1}}}{{{a}_{2}}}=\frac{c}{6},\,\,\frac{{{b}_{1}}}{{{b}_{2}}}=\frac{-1}{-2}=\frac{1}{2},\,\frac{{{c}_{1}}}{{{c}_{2}}}=\frac{-3}{-4}=\frac{3}{4}.\]
    So,       \[\frac{{{b}_{1}}}{{{b}_{2}}}\ne \frac{{{c}_{1}}}{{{c}_{2}}}\]
    So, there will be no value of c for which the pair of equations will have infinitely many solutions.


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