9th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
    What is the LCM of \[{{\mathbf{x}}^{\mathbf{2}}}\mathbf{-1,}\]\[{{\mathbf{x}}^{\mathbf{2}}}\mathbf{-4x+3}\] and \[{{\mathbf{x}}^{\mathbf{2}}}\mathbf{+3x+2?}\]

    A)  \[\left( x+3 \right)\left( x+1 \right)\]         

    B)  \[\left( {{x}^{2}}-1 \right)\left( x+2 \right)\left( x-3 \right)\]

    C)  \[\left( x-1 \right)\left( x-2 \right)\left( x-3 \right)\]            

    D)  \[\left( {{x}^{2}}-1 \right)\left( x+2 \right)\left( x+3 \right)\]

    Correct Answer: B

    Solution :

    (b) (i) \[{{x}^{2}}-1={{x}^{2}}-{{\left( -1 \right)}^{2}}=(x-1)(x+1)\] (ii) \[{{x}^{2}}-4x+3={{x}^{2}}-3x-x+3\] \[=x\left( x-3 \right)-1\left( x-3 \right)=\left( x-3 \right)\left( x-1 \right)\] (iii)\[{{x}^{2}}+3x+2={{x}^{2}}+2x+x+2\] \[=x\left( x+2 \right)+1\left( x+2 \right)=\left( x+2 \right)\left( x+1 \right)\] \[LCM=\left( x-1 \right)\left( x+1 \right)\left( x+2 \right)\left( x-3 \right)\]


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