10th Class Mathematics Pair of Linear Equations in Two Variables Question Bank MCQs - Pair of Linear Equations in Two Variables

  • question_answer
    Solve the following system of linear equations \[ax+by\text{ }-a+b=0\]and   \[bx-ay-a-b=0\]. The value of x and y are

    A) 1, -1

    B) -1, 1

    C) 1, 0

    D) 0, 2

    Correct Answer: A

    Solution :

    The given system can be rewritten as
    \[ax+by=a-b\]                    ...(i)
    and      \[bx-ay=a+b\]                ...(ii)
    From Eq. (i), we get
    \[by=a-b-ax\]
    \[\Rightarrow \,\,\,\,y=\frac{a-b-ax}{b}\]               … (iii)
    On substituting the value of y in Eq. (ii), we get
    \[bx-a\left[ \frac{a-b-ax}{b} \right]=a+b\]
    \[\Rightarrow \,\,\,{{b}^{2}}x-a\left( a-b-ax \right)=b\left( a+b \right)\]
    [multiplying both sides by b]
    \[\Rightarrow \,\,\,{{b}^{2}}x-{{a}^{2}}+ab+{{a}^{2}}x=ab+{{b}^{2}}\]
    \[\Rightarrow \,\,\,\left( {{b}^{2}}+{{a}^{2}} \right)x=ab+{{b}^{2}}+{{b}^{2}}-ab\]
    \[\Rightarrow \,\,\,x=\frac{{{a}^{2}}+{{b}^{2}}}{{{a}^{2}}+{{b}^{2}}}=1\]
    On substituting x = 1 in Eq. (iii), we get
    \[y=\frac{a-b-a}{b}\,\,\Rightarrow y=\frac{-b}{b}=-1\]
    Hence, solution of the given system is x = 1 and y = - 1.


You need to login to perform this action.
You will be redirected in 3 sec spinner