10th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
    If 1 and \[-1\] are zeroes of polynomial \[L{{x}^{4}}+M{{x}^{3}}+N{{x}^{2}}+Rx+P,\]then Find:
    (i) \[L+N+P\]
    (ii) \[M+R\]
    (iii) \[{{M}^{3}}+{{R}^{3}}\]

    A)  i-1                   ii-1       iii-\[-1\]

    B)         i-0                   ii-\[-1\] iii-0

    C)         i-0                   ii-0      iii-0

    D)         i\[-1\]              ii-1      iii-1

    Correct Answer: C

    Solution :

    Since, 1 and \[-1\] are zeroes of \[L{{x}^{4}}+M{{x}^{3}}+N{{x}^{2}}+Rx+P.\] \[\therefore \]    \[L+M+N+R+P=0\]       ?..(1) and \[L-M+N-R+P=0\]            ?..(2) Adding (1) and (2), we get \[2L+2N+2P=0\,\,\Rightarrow \,\,L+N+P=0\] Subtracting (1) from (2), we get \[-2M-2R=0\]  \[\Rightarrow \] \[M+R=0\] Now, \[{{(M+R)}^{3}}=0\]         \[(\because \,\,\,M+R=0)\] \[\Rightarrow \]            \[{{M}^{3}}+{{R}^{3}}+3MR(M+R)=0\] \[\Rightarrow \]\[{{M}^{3}}+{{R}^{3}}+3MR\times 0=0\] \[[\because \,\,M+R=0]\] \[\Rightarrow \]            \[{{M}^{3}}+{{R}^{3}}=0\]


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