Railways Sample Paper RRB (Group D) Sample Test Paper-10

  • question_answer
    If\[(x-\,2)\]and\[(x+3)\]are the factors of the equation \[{{x}^{2}}+{{k}_{1}}x+{{k}_{2}}=0\]Then what are the values of \[{{k}_{1}}\]and\[{{k}_{2}}\]?

    A)  \[(x-\,2)\]          

    B)  \[{{k}_{1}}=1,\,{{k}_{2}}=-\,6\]

    C)  \[{{k}_{1}}=1,\,{{k}_{2}}=-\,6\]

    D)  \[{{k}_{1}}=6,\,{{k}_{2}}=-\,1\]

    Correct Answer: B

    Solution :

    [b] \[\therefore \,\,\,If\,x-\,2=0\] \[\therefore \,\,\,x=2\] \[then,\] \[{{x}^{2}}+{{k}_{1}}x+{{k}_{2}}=0\] \[{{(2)}^{2}}+{{k}_{1}}\times 2+{{k}_{2}}=0\] \[2{{k}_{1}}+{{k}_{2}}=-4\]               ?. (i) \[If\,\,x+3=0\] \[\therefore x=-\,3\] \[then,\,\] \[{{x}^{2}}+{{k}_{1}}x+{{k}_{2}}=0\] \[{{(-\,3)}^{2}}+{{k}_{1}}x-\,3+{{k}_{2}}=0\] \[\therefore 3{{k}_{1}}-\,{{k}_{2}}=9\]              ?. (ii) From equation (i) and (ii), We get \[{{k}_{1}}\]\[=1\] and \[{{k}_{2}}\]


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