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The distance of the origin from the cetroid of the triangle whose two sides have the equations \mathrm{x-2 y+1=0 \text { and } 2 x-y-1=0} and whose orthocentre is \mathrm{\left(\frac{7}{3}, \frac{7}{3}\right)} is:

Option: 1

\sqrt{2}


Option: 2

2


Option: 3

2\sqrt{2}


Option: 4

4


Answers (1)

best_answer

Altitude \mathrm{BD} is perpendicular to  \mathrm{A C \quad(x-2 y+1=0)}\\

\mathrm{\therefore\: Let \: B D\: is \: 2 x+y+\lambda=0}

It passes through \mathrm{D}

\mathrm{\therefore \frac{14}{3}+\frac{7}{3}+\lambda=0} \\

\mathrm{\Rightarrow \lambda=-7 }\\

\mathrm{\therefore \text { BD is } 2 x+y-7=0}

Solving it with equation of \mathrm{AB} we get \mathrm{B(2,3)}

Similarly we can get coordinates of \mathrm{C} as \mathrm{(3,2)}

Centroid of  \mathrm{\Delta ABC}

\mathrm{=\left(\frac{1+2+3}{3}, \frac{1+3+2}{3}\right)} \\

\mathrm{=(2,2)}

Distance of centroid from origin

\mathrm{=\sqrt{4+4}=2 \sqrt{2}}

Hence answer is option 3

Posted by

Shailly goel

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