CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2006

  • question_answer
    If \[a\,|(b+c)\] and \[\,|(b-c)\] where \[a,\,b,\,c\,\in N\] then:

    A)  \[{{b}^{2}}\equiv {{c}^{2}}(\bmod \,{{a}^{2}})\]               

    B)  \[{{b}^{2}}\equiv {{c}^{2}}(\bmod \,{{a}^{2}})\]

    C)  \[{{a}^{2}}\equiv {{b}^{2}}(\bmod \,{{c}^{2}})\]               

    D)  \[{{c}^{2}}\equiv {{a}^{2}}(\bmod \,{{b}^{2}})\]

    Correct Answer: A

    Solution :

    Since a  \[a|(b+c)\]and \[a|(b-c)\] \[\Rightarrow \]               \[\frac{b+c}{a}\] and \[\frac{b-c}{a}\] \[\therefore \]  \[\frac{b+c}{a}.\frac{b-c}{a}=\frac{{{b}^{2}}-{{c}^{2}}}{{{a}^{2}}}\] \[\Rightarrow \]               \[{{a}^{2}}|({{b}^{2}}-{{c}^{2}})\] \[\Rightarrow \]               \[{{b}^{2}}={{c}^{2}}(\bmod \,{{a}^{2}})\]


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