JEE Main & Advanced Mathematics Straight Line Question Bank Mock Test - Straight Lines

  • question_answer
    The equation of the straight line passing through the point (4, 3) and making intercepts on the coordinate axes, whose sum is-1, is

    A)  \[\frac{x}{2}+\frac{y}{3}=-1\] and \[\frac{x}{-2}+\frac{y}{1}=-1\]

    B)  \[\frac{x}{2}-\frac{y}{3}=-1\] and \[\frac{x}{-2}+\frac{y}{1}=-1\]

    C)  \[\frac{x}{2}+\frac{y}{3}=1\] and \[\frac{x}{2}+\frac{y}{3}=1\]

    D)  \[\frac{x}{2}-\frac{y}{3}=1\] and \[\frac{x}{-2}+\frac{y}{1}=1\]

    Correct Answer: D

    Solution :

    [d] Let a and b the intercepts on the coordinate axes. Given a+b=-1 \[\Rightarrow b=-a-1=-(a+1)\] The equation of the line is \[x/a+y/b=1\] \[\Rightarrow \frac{x}{a}-\frac{y}{a+1}=1\]                                ...(i) Since this line passes through (4, 3), \[\frac{4}{a}-\frac{3}{a+1}=1\] \[\Rightarrow \frac{4a+4-3a}{a(a+1)}=1\] \[\Rightarrow a+4={{a}^{2}}+a\] \[\Rightarrow {{a}^{2}}=4\Rightarrow a=\pm 2\] Therefore, the equation of the line [from (i)] is \[\frac{x}{2}-\frac{y}{3}=1\] and \[\frac{x}{-2}+\frac{y}{1}=1\]


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