JCECE Engineering JCECE Engineering Solved Paper-2002

  • question_answer
    Distance between the lines \[5x+3y-7=0\] and\[15x+9y+14=0\] is:

    A) \[\frac{35}{\sqrt{34}}\]                 

    B) \[\frac{1}{3\sqrt{34}}\]

    C) \[\frac{35}{3\sqrt{34}}\]                              

    D)  \[\frac{35}{2\sqrt{34}}\]

    Correct Answer: C

    Solution :

    Given lines are \[5x+3y-7=0\]and\[15x+9y+14=0\] The distance from origin to the lines are                 \[{{d}_{1}}=\frac{0+7-7}{\sqrt{{{5}^{2}}+{{3}^{2}}}}=\frac{-7}{\sqrt{34}}\] and        \[{{d}_{2}}=\frac{0+0+14}{\sqrt{225+81}}=\frac{14}{\sqrt{306}}=\frac{14}{3\sqrt{34}}\] Since, the distance is on opposite sign, it means that the given lines are on opposite side of the origin, therefore the distance between them is                 \[{{d}_{1}}+{{d}_{2}}=\frac{7}{\sqrt{34}}+\frac{14}{3\sqrt{34}}=\frac{35}{3\sqrt{34}}\] Alternative Solution: Given lines are                    \[5x+3y-7=0\] and        \[15x+9y+14=0\] or            \[5x+3y+\frac{14}{3}=0\] Since, the given lines are parallel, therefore the distance between them is                 \[d=\frac{|{{c}_{1}}-{{c}_{2}}|}{\sqrt{{{a}^{2}}+{{b}^{2}}}}=\frac{|-7-\frac{14}{3}|}{\sqrt{{{5}^{2}}+{{3}^{2}}}}\]                    \[=\frac{35}{3\sqrt{34}}\] Note: Let\[ax+by+{{c}_{1}}=0\]and\[ax+by+{{c}_{2}}=0\] are two parallel lines, then the distance between them is                 \[d=\frac{{{c}_{1}}-{{c}_{2}}}{\sqrt{{{a}^{2}}+{{b}^{2}}}}\]


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