JEE Main & Advanced Mathematics Straight Line Question Bank Slope of line, Equation of line in different forms

  • question_answer
    The equation of the line which makes right angled triangle with axes whose area is 6 sq. units and whose hypotenuse is of 5 units, is 

    A)            \[\frac{x}{4}+\frac{y}{3}=\pm \ 1\]                                        

    B)            \[\frac{x}{4}-\frac{y}{3}=\pm \ 3\]

    C)            \[\frac{x}{6}+\frac{y}{1}=\pm \ 1\]                                        

    D)            \[\frac{x}{1}-\frac{y}{6}=\pm \ 1\]

    Correct Answer: A

    Solution :

               If the line is \[\frac{x}{a}+\frac{y}{b}=1\], then the intercepts on the axes are \[a\] and \[b\].                    Therefore the area is \[\frac{1}{2}|a\times b|=6\Rightarrow |ab|=12\]  ?..(i)                    and hypotenuse is 5, therefore \[{{a}^{2}}+{{b}^{2}}=25\]                 ?..(ii)                    On solving (i) and (ii), we get                    \[a=\pm 4\]or \[\pm 3\]and \[b=\pm 3\]or \[\pm 4\]                    Hence equation of line is \[\pm \frac{x}{4}\pm \frac{y}{3}=1\]or \[\pm \frac{x}{3}\pm \frac{y}{4}=1\].               Trick: Check with options. Obviously, the line \[\frac{x}{4}+\frac{y}{3}=\pm 1\] satisfies both the conditions.


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