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 If a variable plane, at a distance of 3 units from the origin, intersects the coordinate axes at A, B and C, then the locus of the centroid of ABC is :

 

  • Option 1)

    \frac{1}{x^{2}}+\frac{1}{y^{2}}+\frac{1}{z^{2}}=1

  • Option 2)

    \frac{1}{x^{2}}+\frac{1}{y^{2}}+\frac{1}{z^{2}}=3

  • Option 3)

    \frac{1}{x^{2}}+\frac{1}{y^{2}}+\frac{1}{z^{2}}=\frac{1}{9}

  • Option 4)

    \frac{1}{x^{2}}+\frac{1}{y^{2}}+\frac{1}{z^{2}}=9

 

Answers (1)

best_answer

As we learnt

Intercept form -

\frac{x}{a}+\frac{y}{b}+\frac{z}{c}= 1

- wherein

Let the plane cuts the coordinate axis at A\left ( a,0,0 \right ),B\left ( 0,b,0 \right )\, and \: C\left ( 0,0,c \right )

 

 

 

 

Centroid of triangle -

\left ( \frac{x_{1}+x_{2}+x_{3}}{3}, \frac{y_{1}+y_{2}+y_{3}}{3}, \frac{z_{1}+z_{2}+z_{3}}{3} \right )

- wherein

 

 

Distance of a point from plane (Cartesian form) -

The length of perpendicular from P(x_{1},y_{1},z_{1}) to the plane

ax+by+cz+d= 0 is given by  \frac{\left [ ax_{1}+by_{1} +cz_{1}+d\right ]}{\left | \sqrt{a^{2}+b^{2}+c^{2}} \right |}

 

-

 

 \frac{x}{a}+\frac{y}{b}+\frac{z}{c}= 1

where,\frac{1}{\sqrt{\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}}}= 3

\Rightarrow {\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}}= \frac{1}{9}

G=\left (h_3k,l \right )= \left ( \frac{a}{3},\frac{b}{3},\frac{c}{3} \right )

So, \frac{1}{9h^2}+\frac{1}{9k^2}+\frac{1}{9l^2}=\frac{1}{9}

\Rightarrow \frac{1}{h^2}+\frac{1}{k^2}+\frac{1}{l^2}=1

\Rightarrow \frac{1}{x^2}+\frac{1}{y^2}+\frac{1}{z^2}=1

 

 

 

 


Option 1)

\frac{1}{x^{2}}+\frac{1}{y^{2}}+\frac{1}{z^{2}}=1

Option 2)

\frac{1}{x^{2}}+\frac{1}{y^{2}}+\frac{1}{z^{2}}=3

Option 3)

\frac{1}{x^{2}}+\frac{1}{y^{2}}+\frac{1}{z^{2}}=\frac{1}{9}

Option 4)

\frac{1}{x^{2}}+\frac{1}{y^{2}}+\frac{1}{z^{2}}=9

Posted by

Aadil

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