CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    If the ratio of the roots of\[{{x}^{2}}+bx+c=0\]and \[{{x}^{2}}+qx+r=0\]is the same, then:

    A)  \[{{r}^{2}}b=q{{c}^{2}}\]

    B)                         \[r{{b}^{2}}=c{{q}^{2}}\]             

    C)         \[{{r}^{2}}c=q{{b}^{2}}\]             

    D)         \[r{{c}^{2}}=b{{q}^{2}}\]

    E)         \[{{r}^{2}}q={{c}^{2}}b\]

    Correct Answer: B

    Solution :

                    Let\[\alpha ,\beta \]be the roots of\[{{x}^{2}}+bx+c=0\]and \[\alpha ,\beta \]are the roots of\[{{x}^{2}}+qx+r=0,\]then \[\alpha +\beta =b,\alpha \beta =c,\alpha +\beta =-q,\alpha \beta =r\]It is given that\[\frac{\alpha }{\beta }=\frac{\alpha }{\beta }\] \[\Rightarrow \]               \[\frac{\alpha +\beta }{\alpha -\beta }=\frac{\alpha +\beta }{\alpha -\beta }\] \[\Rightarrow \]               \[\frac{{{(\alpha +\beta )}^{2}}}{{{(\alpha -\beta )}^{2}}}=\frac{{{(\alpha +\beta )}^{2}}}{{{(\alpha -\beta )}^{2}}}\] \[\Rightarrow \]               \[\frac{{{b}^{2}}}{{{b}^{2}}-4c}=\frac{{{q}^{2}}}{{{q}^{2}}-4r}\] \[\Rightarrow \]               \[{{b}^{2}}r={{q}^{2}}c\]


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