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

  • question_answer
            Find the conditions to be satisfied by coefficients for which the following pair of equations \[\text{ax}+\text{by}+\text{c}=0,\] \[dx+ey+f=0\]represent coincident lines.

    A) \[ab=ed;\,\,bf=ce\]

    B) \[ae=bd;\,\,bc=ef\]

    C) \[ad=bc,\,\,bf=ce\]

    D) \[ae=bd,\,\,bf=ce\]

    Correct Answer: D

    Solution :

    [d] The given pair of equations is                         
    \[ax+by+c=0\]and \[dx+ey+f=0\]
    For coincident lines:   
    \[\frac{{{a}_{1}}}{{{a}_{2}}}=\frac{{{b}_{1}}}{{{b}_{2}}}=\frac{{{c}_{1}}}{{{c}_{2}}}\,\,\,\,\,\,\,\,\,\Rightarrow \,\,\,\,\,\,\,\,\frac{a}{d}=\frac{b}{e}=\frac{c}{f}\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,ae=bd\]
    and       \[bf=ce\]


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