Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section A

Chapter

Applications of Derivatives

Question:

Match List I with List II

LIST I

LIST II

A. Slope of the tangent to curve $x^3 - 2x$ at $x=2$

I. -81

B. Slope of line passing through the points (0, 2) and (5,-6)

II. 10

C. Point at which the tangent to the curve $y=\sqrt{4x-3}$ has its slope $\frac{2}{3}$

III. $-\frac{8}{5}$

D. Slope of normal to the curve $y =\frac{x-2}{x-1}$ at x = 10

IV. (3,3)

Choose the correct answer from the options given below:

Options:

A-II, B-III, C-IV, D-I

A-III, B-II, C-I, D-IV

A-III, B-I, C-IV, D-II

A-I, B-IV, C-II, D-III

Correct Answer:

A-II, B-III, C-IV, D-I

Explanation:

A. $y=x^3 - 2x$

$y'=3x^2-2$

Slope at $x = 2$

$y'|_{x=2}=3×2^2-2=10$

B. points $P(0, 2)$ and $Q(5,-6)$

Slope → $\frac{-6-2}{5-0}=-\frac{8}{5}$

C. $y=\sqrt{4x-3}$ for $y'=\frac{2}{3}$

$y'=\frac{1}{2}\frac{4}{\sqrt{4x-3}}⇒\frac{2}{3}=\frac{4}{2\sqrt{4x-3}}$

so $\sqrt{4x-3}=3=y$

$⇒4x-3=9=4x=12⇒x=3$  $⇒(3,3)$

D. $y =\frac{x-2}{x-1}$, so $y'=-\frac{(x-2)+(x-1)}{(x-1)^2}$

$y'=\frac{+1}{(x-1)^2}$  (slope of tangent)

slope of normal = $-(x-1)^2$ at $x = 10$

Slope of normal = $-(10-1)^2=-81$