Question

The equation of the normal to the curve $$y = \left| {{x^2} - \left| x \right|} \right|{\text{ at }}x = - 2.$$

A. $$3y = x + 8$$  
B. $$x = 3y + 4$$
C. $$y = 2x + 8$$
D. $$y = 3x$$
Answer :   $$3y = x + 8$$
Solution :
In the neighborhood of $$x = - 2,\,y = {x^2} + x.$$
Hence, the point on curve is $$\left( { - 2,\,2} \right).$$
$$\frac{{dy}}{{dx}} = 2x + 1{\text{ or }}{\left. {\frac{{dy}}{{dx}}} \right|_{x = - 2}} = - 3$$
So, the slope of the normal at $$\left( { - 2,\,2} \right)$$  is $$\frac{1}{3}$$
Hence, the equation of the normal is $$\frac{1}{3}\left( {x + 2} \right) = y - 2{\text{ or }}3y = x + 8.$$

Releted MCQ Question on
Calculus >> Application of Derivatives

Releted Question 1

If  $$a + b + c = 0,$$    then the quadratic equation $$3a{x^2}+ 2bx + c = 0$$     has

A. at least one root in $$\left[ {0, 1} \right]$$
B. one root in $$\left[ {2, 3} \right]$$  and the other in $$\left[ { - 2, - 1} \right]$$
C. imaginary roots
D. none of these
Releted Question 2

$$AB$$  is a diameter of a circle and $$C$$ is any point on the circumference of the circle. Then

A. the area of $$\Delta ABC$$  is maximum when it is isosceles
B. the area of $$\Delta ABC$$  is minimum when it is isosceles
C. the perimeter of $$\Delta ABC$$  is minimum when it is isosceles
D. none of these
Releted Question 3

The normal to the curve $$x = a\left( {\cos \theta + \theta \sin \theta } \right),y = a\left( {\sin \theta - \theta \cos \theta } \right)$$        at any point $$'\theta '$$ is such that

A. it makes a constant angle with the $$x - $$axis
B. it passes through the origin
C. it is at a constant distance from the origin
D. none of these
Releted Question 4

If $$y = a\ln x + b{x^2} + x$$     has its extremum values at $$x = - 1$$  and $$x = 2,$$  then

A. $$a = 2,b = - 1$$
B. $$a = 2,b = - \frac{1}{2}$$
C. $$a = - 2,b = \frac{1}{2}$$
D. none of these

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