9th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
    Study the given statements.
    Statement I: \[\frac{{{({{a}^{2}}-{{b}^{2}})}^{3}}+{{({{b}^{2}}-{{c}^{2}})}^{3}}+{{({{c}^{2}}-{{a}^{2}})}^{3}}}{{{(a+b)}^{3}}{{(b+c)}^{3}}+{{(c+a)}^{3}}}\]
    Statement II:  \[{{a}^{2}}+{{b}^{2}}+{{c}^{2}}-ab-bc-ca\]            \[=\frac{1}{2}\left[ {{(a-b)}^{2}}+{{(b-c)}^{2}}+{{(c-a)}^{2}} \right]\]
    Which of the following options holds?

    A)  Both Statement-I and Statement-II are true.

    B)  Statement-I is true but Statement-II is false.

    C)  Statement-I is false but Statement-II is true.

    D)  Both Statement-I and Statement-II are false.

    Correct Answer: C

    Solution :

    Statement - I: We have, \[\frac{{{({{a}^{2}}-{{b}^{2}})}^{3}}+({{b}^{2}}-{{c}^{2}})+{{({{c}^{2}}-{{a}^{2}})}^{3}}}{{{(a+b)}^{3}}+{{(b+c)}^{3}}+{{(c+a)}^{3}}}\] \[\frac{\begin{align}   & ({{a}^{2}}-{{b}^{2}}+{{b}^{2}}-{{c}^{2}}+{{c}^{2}}-{{a}^{2}})[{{({{a}^{2}}-{{b}^{2}})}^{2}}+{{({{b}^{2}}-{{c}^{2}})}^{2}} \\  & +{{({{c}^{2}}-{{a}^{2}})}^{2}}-({{a}^{2}}-{{b}^{2}})({{b}^{2}}-{{c}^{2}})-({{b}^{2}}-{{c}^{2}})({{c}^{2}}-{{a}^{2}}) \\  & -{{({{c}^{2}}-{{a}^{2}})}^{2}}({{a}^{2}}-{{b}^{2}})]+3({{a}^{2}}-{{b}^{2}})({{b}^{2}}-{{c}^{2}})({{c}^{2}}-{{a}^{2}}) \\ \end{align}}{\begin{align}   & (a+b+b+c+c+a)[{{(a+b)}^{2}}+{{(b+c)}^{2}}+{{(c+a)}^{2}} \\  & -(a+b)(b+c)-(b+c)(c+a)-(c+a) \\  & (a+b)]+3(a+b)(b+c)(c+a) \\ \end{align}}\] Statement -II: We have, \[{{a}^{2}}+{{b}^{2}}+{{c}^{2}}-ab-bc-ac=\frac{1}{2}\{2a-2{{b}^{2}}\] \[+2{{c}^{2}}-2ab-2bc-2ac\}\] \[=\frac{1}{2}[{{(a-b)}^{2}}+{{(b-c)}^{2}}+{{(c-a)}^{2}}]\] \[\therefore \]Statement - I is false but Statement -II is true.


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