Question

The normal to the curve, $${x^2} + 2xy - 3{y^2} = 0,$$    at $$\left( {1,\,1} \right)$$

A. meets the curve again in the third quadrant.
B. meets the curve again in the fourth quadrant.  
C. does not meet the curve again.
D. meets the curve again in the second quadrant.
Answer :   meets the curve again in the fourth quadrant.
Solution :
Given curve is
$${x^2} + 2xy - 3{y^2} = 0.....(1)$$
Differentiate w.r.t. $$x,\,\,\,2x + 2x\frac{{dy}}{{dx}} + 2y - 6y\frac{{dy}}{{dx}} = 0$$
$${\left( {\frac{{dy}}{{dx}}} \right)_{\left( {1,\,1} \right)}} = 1$$
Equation of normal at $$\left( {1,\,1} \right)$$  is
$$y = 2 - x.....(2)$$
Solving equation (1) and (2), we get $$x=1 ,\,3$$
Point of intersection $$\left( {1,\,1} \right),\,\left( {3,\, - 1} \right)$$
Normal cuts the curve again in 4th quadrant.

Releted MCQ Question on
Geometry >> Locus

Releted Question 1

The equation $$\frac{{{x^2}}}{{1 - r}} - \frac{{{y^2}}}{{1 + r}} = 1,\,\,\,r > 1$$       represents :

A. an ellipse
B. a hyperbola
C. a circle
D. none of these
Releted Question 2

The equation $$2{x^2} + 3{y^2} - 8x - 18y + 35 = k$$       represents :

A. no locus if $$k>0$$
B. an ellipse if $$k<0$$
C. a point if $$k=0$$
D. a hyperbola if $$k>0$$
Releted Question 3

If $$a>2b>0$$    then the positive value of $$m$$ for which $$y = mx - b\sqrt {1 + {m^2}} $$     is a common tangent to $${x^2} + {y^2} = {b^2}$$   and $${\left( {x - a} \right)^2} + {y^2} = {b^2}$$    is :

A. $$\frac{{2b}}{{\sqrt {{a^2} - 4{b^2}} }}$$
B. $$\frac{{\sqrt {{a^2} - 4{b^2}} }}{{2b}}$$
C. $$\frac{{2b}}{{a - 2b}}$$
D. $$\frac{b}{{a - 2b}}$$
Releted Question 4

The locus of the mid-point of the line segment joining the focus to a moving point on the parabola $${y^2} = 4ax$$   is another parabola with directrix :

A. $$x = - a$$
B. $$x = - \frac{a}{2}$$
C. $$x = 0$$
D. $$x = \frac{a}{2}$$

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Locus


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