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8th Class Mathematics Factorisation Question Bank Factorisation

  • question_answer
    If \[({{x}^{2}}+3x+5)\,\,({{x}^{2}}-3x+5)={{m}^{2}}-{{n}^{2}},\]what is the value of m?

    A)  \[{{x}^{2}}-3x\]                               

    B)  \[3x\]                  

    C)  \[{{x}^{2}}+5\]

    D)         \[{{x}^{2}}+3x\]

    Correct Answer: C

    Solution :

    \[({{x}^{2}}+3x+5)\,\,({{x}^{2}}-3x+5)\] \[=({{x}^{2}}+5+3x)\,\,({{x}^{2}}+5-3x)\] \[={{({{x}^{2}}+5)}^{2}}-{{(3x)}^{2}}={{m}^{2}}-{{n}^{2}}\]                 \[\therefore \]  \[m\,={{x}^{2}}+5\]


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