Question

If the sum of the slopes of the lines given by $${x^2} - 2cxy - 7{y^2} = 0$$     is four times their product $$c$$ has the value-

A. $$-2$$
B. $$-1$$
C. 2  
D. 1
Answer :   2
Solution :
Let the lines be $$y = {m_1}x$$   and $$y = {m_2}x$$   then
$$\eqalign{ & {m_1} + {m_2} = - \frac{{2c}}{7}{\text{ and }}{m_1}{m_2} = - \frac{1}{7} \cr & {\text{Given }}{m_1} + {m_2} = 4\,{m_1}{m_2} \cr & \Rightarrow \frac{{2c}}{7} = - \frac{4}{7}\,\,\,\, \Rightarrow c = 2 \cr} $$

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

Practice More Releted MCQ Question on
Straight Lines


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