JCECE Engineering JCECE Engineering Solved Paper-2011

  • question_answer
    If\[a\ne p,\,\,b\ne q,\,\,c\ne r\]and\[\left| \begin{matrix}    p & b & c  \\    a & q & c  \\    a & b & r  \\ \end{matrix} \right|=0\]. Then, the value of\[\frac{p}{p-a}+\frac{q}{q-b}+\frac{r}{r-c}\]is

    A) \[0\]                                     

    B) \[1\]

    C) \[-1\]                                    

    D) \[2\]

    Correct Answer: D

    Solution :

    We have,\[\left| \begin{matrix}    p & b & c  \\    a & q & c  \\    a & b & r  \\ \end{matrix} \right|=0\] \[\Rightarrow \]               \[\left| \begin{matrix}    p & b & c  \\    a-p & q-b & 0  \\    0 & b-q & r-c  \\ \end{matrix} \right|=0\] [Applying\[{{R}_{3}}\to {{R}_{3}}-{{R}_{2}}\]and\[{{R}_{2}}\to {{R}_{2}}-{{R}_{1}}]\] \[\Rightarrow \]               \[\left| \begin{matrix}    \frac{p}{p-a} & \frac{b}{q-b} & \frac{c}{r-c}  \\    -1 & 1 & 0  \\    0 & -1 & 1  \\ \end{matrix} \right|=0\] \[\Rightarrow \]               \[\frac{p}{p-a}+\frac{b}{q-b}+\frac{c}{r-c}=0\] \[\Rightarrow \]               \[\frac{p}{p-a}+\left( \frac{q}{q-b}-1 \right)+\left( \frac{r}{r-c}-1 \right)=0\] \[\Rightarrow \]               \[\frac{p}{p-a}+\frac{q}{q-b}+\frac{r}{r-c}=0\]


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