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

  • question_answer
    The equation of the line bisecting the line segment joining the points (a, b) and \[({a}',\ {b}')\]at right angle, is

    A)            \[2(a-{a}')x+2(b-{b}')y={{a}^{2}}+{{b}^{2}}-{{{a}'}^{2}}-{{{b}'}^{2}}\]

    B)            \[(a-{a}')x+(b-{b}')y={{a}^{2}}+{{b}^{2}}-{{{a}'}^{2}}-{{{b}'}^{2}}\]

    C)            \[2(a-{a}')x+2(b-{b}')y={{{a}'}^{2}}+b{{'}^{2}}-{{a}^{2}}-{{b}^{2}}\]

    D)            None of these

    Correct Answer: A

    Solution :

               \[m=\frac{-1}{\frac{{b}'-b}{{a}'-a}}=\frac{{a}'-a}{b-{b}'}\]. Midpoint is \[\left( \frac{a+{a}'}{2},\frac{b+{b}'}{2} \right)\]                    Therefore equation of line is \[y-\left( \frac{b+{b}'}{2} \right)=\frac{{a}'-a}{b-{b}'}\left( x-\frac{a+{a}'}{2} \right)\]                    \[\Rightarrow 2(b-{b}')y+2(a-{a}')x-{{b}^{2}}+{{{b}'}^{2}}-{{a}^{2}}+{{{a}'}^{2}}=0\].


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