Subject

    Quantitative Aptitude

    Topic

    Simplification

    Find the value of the expression: 3  +  53  −  5−  3  −  53  +  5=  ?\frac{{3\; + \;\sqrt 5 }}{{3\; - \;\sqrt 5 }} - \;\frac{{3\; - \;\sqrt 5 }}{{3\; + \;\sqrt 5 }} = \;?

    ক)
    3√5
    খ)
    -4√5
    গ)
    -3√5
    ঘ)
    4√5
    ঙ)
    None of these

    Explanation

    Given expression is, 3  +  53  −  5−  3  −  53  +  5=  (3  +  5)2−  (3  −  √5)2(3  −  5)(3+5)=  (9  +  5  +  65)−  (9  +  5  −6  5)(3)2−  (5)2=12  59−5\begin{array}{l} \frac{{3\; + \;\sqrt 5 }}{{3\; - \;\sqrt 5 }} - \;\frac{{3\; - \;\sqrt 5 }}{{3\; + \;\sqrt 5 }}\\ = \;\frac{{{{\left( {3\; + \;\sqrt 5 } \right)}^2} - \;{{\left( {3\; - \;\surd 5} \right)}^2}}}{{\left( {3\; - \;\sqrt 5 } \right)\left( {3 + \sqrt 5 } \right)}}\\ = \;\frac{{\left( {9\; + \;5\; + \;6\sqrt 5 } \right) - \;\left( {9\; + \;5\; - 6\;\sqrt 5 } \right)}}{{{{\left( 3 \right)}^2} - \;{{\left( {\sqrt 5 } \right)}^2}}}\\ = \frac{{12\;\sqrt 5 }}{{9 - 5}} \end{array} = 12√5/4 = 3√5

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