SSC Sample Paper Mock Test-5 SSC CGL Tear-II Paper-1

  • question_answer
    The following system of equations have the solution \[ax-by={{a}^{2}}-{{b}^{2}}\]                       ...(i) \[x+y=a+b\]                             ...(ii)

    A)  \[x=a\]and \[y=b\]       

    B)  \[x=-\,\,a\]and \[y=-b\]

    C)  \[x=b\]and \[y=a\]       

    D) \[x=-\,\,b\]and \[y=-\,\,a\]

    Correct Answer: A

    Solution :

    Here, in Eq. (i)
    \[{{a}_{1}}=a,\]\[{{b}_{1}}=-\,b,\]\[{{c}_{1}}=-\,\,({{a}^{2}}-{{b}^{2}})\]and
                In Eq. (ii) \[{{a}_{2}}=1,\]\[{{b}_{2}}=1,\]\[{{c}_{2}}=-\,(a+b)\]
    So,       \[x=\frac{{{b}_{1}}{{c}_{2}}-{{b}_{2}}{{c}_{1}}}{{{a}_{1}}{{b}_{2}}-{{a}_{2}}{{b}_{1}}}=\frac{(b)(a+b)+(1)({{a}^{2}}-{{b}^{2}})}{a\,\,(1)-(1)(-b)}\]
    \[x=\frac{ab+{{b}^{2}}+{{a}^{2}}-{{b}^{2}}}{a+b}=\frac{a\,\,(a+b)}{(a+b)}=a\]
    and       \[y=\frac{{{c}_{1}}{{a}_{2}}-{{c}_{2}}{{a}_{1}}}{{{a}_{1}}{{b}_{2}}-{{a}_{2}}{{b}_{1}}}\]
    \[y=\frac{-\,\,({{a}^{2}}-{{b}^{2}})(1)+(a+b)(a)}{a+b}\]       \[=\frac{b\,\,(a+b)}{(a+b)}=b\]
    So,       \[x=a\]and \[y=b\]is solution.


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