JEE Main & Advanced Mathematics Determinants & Matrices Question Bank System of linear equations, Some special determinants, differentiation and integration of determinants

  • question_answer
    The number of values of k for which the system of equations \[(k+1)x+8y=4k,\] \[kx+(k+3)y=3k-1\] has infinitely many solutions, is [IIT Screening 2002]

    A) 0

    B) 1

    C) 2

    D) Infinite

    Correct Answer: B

    Solution :

    For infinitely many solutions, the two equations must be identical \[\Rightarrow \frac{k+1}{k}=\frac{8}{k+3}=\frac{4k}{3k-1}\] \[\Rightarrow (k+1)(k+3)=8k\] and \[8\,(3k-1)=4k(k+3)\] \[\Rightarrow {{k}^{2}}-4k+3=0\]and \[{{k}^{2}}-3k+2=0\]. By cross multiplication, \[\frac{{{k}^{2}}}{-8+9}=\frac{k}{3-2}=\frac{1}{-3+4}\] \[{{k}^{2}}=1\] and \[k=1\]; \ \[k=1\].


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