BCECE Engineering BCECE Engineering Solved Paper-2015

  • question_answer
    The equation of a straight line passing through the point of intersection of \[x-y+1=0\]and  \[3x+y-5=0\]  and perpendicular to one of them, is

    A)  x + y + 3 = 0       

    B)  x - y - 3 = 0

    C) x-3y-5=0                             

    D) x-3y+5=0

    Correct Answer: D

    Solution :

    The equation of a straight line passing through the point of intersection of x - y +1 = 0 and 3x+y-5=0 is \[(x-y+1)+\lambda (3x+y-5)=0\] or \[x(3\lambda +1)+y(\lambda -1)-(5\lambda -1)=0\]    ? (i) It is perpendicular to 3x + y - 5 = 0. \[\therefore \]  \[-3\times \left( -\frac{3\lambda +1}{\lambda -1} \right)=-1\] \[\Rightarrow \]                               \[\lambda =\frac{-1}{5}\] On putting\[\lambda =-\frac{1}{5}\]in Eq. (i), we get x - 3y + 5 = 0 as the equation of the required line.


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