SSC Sample Paper SSC-CGL TIER - I Sample Test Paper-7

  • question_answer
    What is the LCM of \[{{x}^{2}}+2x-8,{{x}^{3}}-4{{x}^{2}}+4x\]and\[{{x}^{2}}+4x\]?

    A) \[x\left( x+4 \right){{\left( x-2 \right)}^{2}}\]

    B) \[x\left( x+4 \right)\left( x-2 \right)\]

    C) \[x\left( x+4 \right){{\left( x+2 \right)}^{2}}\]

    D) \[x{{\left( x+4 \right)}^{2}}\left( x-2 \right)\]

    Correct Answer: A

    Solution :

    \[{{x}^{2}}+2x-8={{x}^{2}}+4x-2x-8\] =   \[x\left( x+4 \right)-2\left( x+4 \right)=\left( x-2 \right)\left( x+4 \right)\] =   \[{{x}^{3}}-4{{x}^{2}}+4x={{x}^{3}}-2{{x}^{2}}-2{{x}^{2}}+4x\] =   \[{{x}^{2}}(x-2)-2x(x-2)\] =   \[({{x}^{2}}-2x)(x-2)\Rightarrow x(x-2)(x-2)\] =   \[{{x}^{2}}+4x=x\left( x+4 \right)\] Now, LCM of\[({{x}^{2}}+2x-8)\], \[({{x}^{2}}-4{{x}^{2}}+4x)\] and\[\left( {{x}^{2}}+4x \right)=x\left( x-2 \right)\left( x+4 \right)\left( x-2 \right)\] =         \[\mathbf{x}\left( \mathbf{x+4} \right){{\left( \mathbf{x-2} \right)}^{\mathbf{2}}}\]


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