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  3. 9th Class
  4. Mathematics
  5. Linear Equations in Two Variables

9th Class Mathematics Linear Equations in Two Variables Question Bank Linear Equation in two Variables

  • question_answer
    If \[\mathbf{x}+\mathbf{y}-\mathbf{5}=\mathbf{0}\] and \[\mathbf{2x+y-9=0,}\] then \[\mathbf{4}{{\mathbf{x}}^{\mathbf{2}}}\mathbf{+}{{\mathbf{y}}^{\mathbf{2}}}\mathbf{+4xy}\] is equal to

    A)  75                             

    B)  85

    C)  91                             

    D)  81

    Correct Answer: D

    Solution :

    (d): We have, \[x+y-5=0\] \[\Rightarrow ~~~~x+y=5\]                 ...(i) And     \[2x+y-9=0\] \[\Rightarrow ~~~~2x+y=9\]               ....(ii) On solving equation (i) and (ii) we get \[x=4\] and \[y=1\] Now, \[4{{x}^{2}}+{{y}^{2}}+4xy=81\]


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