Question

Let $$A\left( {2,\, - 3} \right)$$   and $$B\left( { - 2,\,3} \right)$$   be vertices of a triangle $$ABC.$$   If the centroid of this triangle moves on the line $$2x +3y =1,$$    then the locus of the vertex $$C$$ is the line-

A. $$3x-2y=3$$
B. $$2x-3y=7$$
C. $$3x+2y=5$$
D. $$2x+3y=9$$  
Answer :   $$2x+3y=9$$
Solution :
Let the vertex $$C$$ be $$\left( {h,\,k} \right),$$   then the centroid of $$\Delta ABC$$   is $$\left( {\frac{{2 - 2 + h}}{3},\,\frac{{ - 3 + 1 + k}}{3}} \right)\,\,{\text{or }}\,\left( {\frac{h}{3},\,\frac{{ - 2 + k}}{3}} \right)$$
It lies on $$2x+3y=1$$
$$\eqalign{ & \Rightarrow \frac{{2h}}{3} - 2 + k = 1 \cr & \Rightarrow 2h + 3k = 9 \cr} $$
$$=$$ Locus of $$C$$ is $$2x+3y=9$$

Releted MCQ Question on
Geometry >> Straight Lines

Releted Question 1

The points $$\left( { - a, - b} \right),\left( {0,\,0} \right),\left( {a,\,b} \right)$$     and $$\left( {{a^2},\,ab} \right)$$  are :

A. Collinear
B. Vertices of a parallelogram
C. Vertices of a rectangle
D. None of these
Releted Question 2

The point (4, 1) undergoes the following three transformations successively.
(i) Reflection about the line $$y =x.$$
(ii) Translation through a distance 2 units along the positive direction of $$x$$-axis.
(iii) Rotation through an angle $$\frac{p}{4}$$ about the origin in the counter clockwise direction.
Then the final position of the point is given by the coordinates.

A. $$\left( {\frac{1}{{\sqrt 2 }},\,\frac{7}{{\sqrt 2 }}} \right)$$
B. $$\left( { - \sqrt 2 ,\,7\sqrt 2 } \right)$$
C. $$\left( { - \frac{1}{{\sqrt 2 }},\,\frac{7}{{\sqrt 2 }}} \right)$$
D. $$\left( {\sqrt 2 ,\,7\sqrt 2 } \right)$$
Releted Question 3

The straight lines $$x + y= 0, \,3x + y-4=0,\,x+ 3y-4=0$$         form a triangle which is-

A. isosceles
B. equilateral
C. right angled
D. none of these
Releted Question 4

If $$P = \left( {1,\,0} \right),\,Q = \left( { - 1,\,0} \right)$$     and $$R = \left( {2,\,0} \right)$$  are three given points, then locus of the point $$S$$ satisfying the relation $$S{Q^2} + S{R^2} = 2S{P^2},$$    is-

A. a straight line parallel to $$x$$-axis
B. a circle passing through the origin
C. a circle with the centre at the origin
D. a straight line parallel to $$y$$-axis

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Straight Lines


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