8th Class Mathematics Algebraic Expressions Question Bank Algebra

  • question_answer
    If \[{{(a+b)}^{2}}={{a}^{2}}+2ab+{{b}^{2}}\], then the value of \[x+\frac{1}{1+\frac{1}{1+\frac{1}{x}}}\]is equal to

    A)  \[{{(a+b)}^{3}}={{a}^{3}}+3{{a}^{2}}b+3a{{b}^{2}}+{{b}^{3}}={{a}^{3}}+{{b}^{3}}+3ab(a+b)\]                       

    B)  \[{{(a-b)}^{3}}={{a}^{3}}-3{{a}^{2}}b+3a{{b}^{2}}-{{b}^{3}}={{a}^{3}}-{{b}^{3}}-3ab(a-b)\]

    C)  \[{{a}^{3}}+{{b}^{3}}=(a+b)({{a}^{2}}-ab+{{b}^{2}})\]                               

    D) none of these

    Correct Answer: A

    Solution :

    \[x+\frac{1}{1+\frac{1}{1+\frac{1}{x}}}=\frac{1}{2}+\frac{1}{1+\frac{1}{1+\frac{1}{2}}}\] \[=\frac{1}{2}+\frac{1}{1+\frac{1}{1+2}}=\frac{1}{2}+\frac{1}{1+\frac{1}{3}}=\frac{1}{2}+\frac{1}{\frac{4}{3}}\] \[=\frac{1}{2}+\frac{3}{4}=\frac{2+3}{4}=\frac{5}{4}\]        


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