CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    If the root of the equation\[\frac{a}{x-a}+\frac{b}{x-b}=1\]are equal in magnitude and opposite in sign, then:

    A)  \[a=b\]               

    B)         \[a+b=1\]

    C)  \[a-b=1\]           

    D)         \[a+b=0\]

    E)  \[a+b=2\]

    Correct Answer: D

    Solution :

    \[\frac{a}{x-a}+\frac{b}{x-b}=1\] \[\Rightarrow \]\[a(x-b)+b(x-a)=(x-a)(x-b)\] \[\Rightarrow \]\[ax-ab+ba-ab={{x}^{2}}-ax-bx+ab\] \[\Rightarrow \]\[{{x}^{2}}-2ax-2bx+3ab=0\] \[\Rightarrow \]\[{{x}^{2}}-2(a+b)x+3ab=0\] Let \[\alpha \]and \[-\alpha \] be roots of above equation \[\therefore \]                  \[\alpha -\alpha =\frac{2(a+b)}{1}\] \[\Rightarrow \]                               \[a+b=0\]


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