Question

$$\mathop {\lim }\limits_{h \to 0} \frac{{f\left( {2h + 2 + {h^2}} \right) - f\left( 2 \right)}}{{f\left( {h - {h^2} + 1} \right) - f\left( 1 \right)}},$$      given that $$f'\left( 2 \right) = 6$$   and $$f'\left( 1 \right) = 4$$

A. does not exist
B. is equal to $$ - \frac{3}{2}$$
C. is equal to $$\frac{3}{2}$$
D. is equal to $$3$$  
Answer :   is equal to $$3$$
Solution :
$${\text{Let }}L = \mathop {\lim }\limits_{h \to 0} \frac{{f\left( {2h + 2 + {h^2}} \right) - f\left( 2 \right)}}{{f\left( {h - {h^2} + 1} \right) - f\left( 1 \right)}}\,\,\,\,\,\,\,\left[ {\frac{0}{0}{\text{form}}} \right]$$
$$\therefore $$ Applying L'Hospital rule, we get
$$\eqalign{ & L = \mathop {\lim }\limits_{h \to 0} \frac{{f'\left( {2h + 2 + {h^2}} \right).\left( {2 + 2h} \right)}}{{f'\left( {h - {h^2} + 1} \right).\left( {1 - 2h} \right)}} \cr & = \frac{{f'\left( 2 \right).2}}{{f'\left( 1 \right).1}} \cr & = \frac{{6 \times 2}}{{4 \times 1}} \cr & = 3 \cr} $$

Releted MCQ Question on
Calculus >> Differentiability and Differentiation

Releted Question 1

There exist a function $$f\left( x \right),$$  satisfying $$f\left( 0 \right) = 1,\,f'\left( 0 \right) = - 1,\,f\left( x \right) > 0$$       for all $$x,$$ and-

A. $$f''\left( x \right) > 0$$   for all $$x$$
B. $$ - 1 < f''\left( x \right) < 0$$    for all $$x$$
C. $$ - 2 \leqslant f''\left( x \right) \leqslant - 1$$    for all $$x$$
D. $$f''\left( x \right) < - 2$$   for all $$x$$
Releted Question 2

If $$f\left( a \right) = 2,\,f'\left( a \right) = 1,\,g\left( a \right) = - 1,\,g'\left( a \right) = 2,$$         then the value of $$\mathop {\lim }\limits_{x \to a} \frac{{g\left( x \right)f\left( a \right) - g\left( a \right)f\left( x \right)}}{{x - a}}$$      is-

A. $$-5$$
B. $$\frac{1}{5}$$
C. $$5$$
D. none of these
Releted Question 3

Let $$f:R \to R$$   be a differentiable function and $$f\left( 1 \right) = 4.$$   Then the value of $$\mathop {\lim }\limits_{x \to 1} \int\limits_4^{f\left( x \right)} {\frac{{2t}}{{x - 1}}} dt$$     is-

A. $$8f'\left( 1 \right)$$
B. $$4f'\left( 1 \right)$$
C. $$2f'\left( 1 \right)$$
D. $$f'\left( 1 \right)$$
Releted Question 4

Let [.] denote the greatest integer function and $$f\left( x \right) = \left[ {{{\tan }^2}x} \right],$$    then:

A. $$\mathop {\lim }\limits_{x \to 0} f\left( x \right)$$     does not exist
B. $$f\left( x \right)$$  is continuous at $$x = 0$$
C. $$f\left( x \right)$$  is not differentiable at $$x =0$$
D. $$f'\left( 0 \right) = 1$$

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Differentiability and Differentiation


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