Continuity and Differentiability

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alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

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New answer posted

a year ago

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A
alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Sol:

New answer posted

a year ago

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A
alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Sol:

Given  that          f(x)=x3−2x2−x+3  in  [0,1](i)  f(x)  is  an    function,  so  it  is  continuous  in  [0,1].(ii)  f'(x)=3x2−4x−1  which  exists  in  (0,1)So,  f(x)  is  differentiable.As  the  above  conditions  are  satisfied,  then  there  must  exist  atleast  one    ∈(0,1)  such  thatf'(c)=f(b)−f(a)b−a⇒  3c2−4c−1=[(1)3−2(1)2−(1)+3]−[0−0−0−3]1−0⇒  3c2−4c−1=(1−2−1+3)−(3)1⇒  3c2−4c−1=1−3⇒3c2−4c−1=−2⇒3c2−4c+1=0   ⇒3c2−3c−c+1=0⇒3c(c−1)−1(c−1)=0   ⇒(c−1)(3c−1)=0⇒    c−1=0    ∴c=1      3c−1=0     ∴c=13∈(0,1)Hence,  Mean  Value  Theorem  is  verified.

New answer posted

a year ago

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A
alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Sol:

New answer posted

a year ago

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A
alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Sol:

G i v e n     t h a t                     y = x ( x − 4 ) , x ∈ [ 0 , 4 ] L e t                                     f ( x ) = x ( x − 4 ) , x ∈ [ 0 , 4 ] (i)  f(x)  being  an  algebraic  polynomial  is  continuous  function  everywhere. S o ,     f ( x ) = x ( x − 4 )     i s     c o n t i n u o u s     x     i n     [ 0 , 4 ] . ( i i )     f ' ( x ) = 2 x − 4     w h i c h     e x i s t s     i n     ( 0 , 4 ) S o , f ( x )     i s     d i f f e r e n t i a b l e . ( i i i )               f ( 0 ) = 0 ( 0 − 4 ) = 0                               f ( 4 ) = 0 ( 4 − 4 ) = 0 ∴                     f ( 0 ) = f ( 4 ) = 0 As  the  above  conditions  are  satisfied,  then  there  must  exist  at  least  one  point  c∈(0,4)  such  that  f'(c)=0 ∴     2 c − 4 = 0                   ⇒ c = 2 ∈ ( 0 , 4 ) Hence,  c=2  is  the  point  in  (0,4)  on  the  given  curve  at  which  the  tangent  is  parallel  to  the x−axis.

New answer posted

a year ago

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A
alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Sol:

G i v e n     t h a t                     y = c o s x − 1     o n     [ 0 , 2 π ] Firstly,  we  have  to  find  a  point  c  on  the  given  curve  y=cosx−1  on  [0,2π]  such  that  the  tangent  at c=0∈[0,2π]  is  parallel  to  x−axis  i.e.,  f'(c)=0  where  f'(c)  is  the  slope  of  the  tangent. S o ,     w e     h a v e     t o     v e r i f y     t h e     R o l l e ' s     T h e o r e m . (i)  y=cosx−1,  is  the  combination  of  cosine  and  constant  functions.  So,  it  is  continuous  on  [0,2π]. ( i i )               d y d x = − s i n x     w h i c h     e x i s t s     i n     ( 0 , 2 π ) S o     i t     i s     d i f f e r e n t i a b l e     o n     ( 0 , 2 π ) . ( i i i )     L e t           f ( x ) = c o s x − 1                               f ( 0 ) = c o s 0 − 1               ⇒ 1 − 1 = 0                         f ( 2 π ) = c o s 2 π − 1         ⇒ 1 − 1 = 0 ∴                           f ( 0 ) = f ( 2 π ) = 0 As  the  above  conditions  are  satisfied,  then  there  lies  a  point  c∈(0,2π)  such  that  f'(c)=0 ∴     − s i n c = 0                   ⇒ s i n c = 0 ∴ c = n π , n ∈ I ⇒ c = π ∈ ( 0 , 2 π ) Hence,  c=π  is  the  point  on  the curve  in  (0,2π)  at  which  the  tangent  is  parallel  to  x−axis.

New answer posted

a year ago

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A
alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Sol:

(i)  f(x)  being  an  algebraic  polynomial  is  continuous  everywhere. ( i i )     f ( x )     m u s t     b e     d i f f e r e n t i a b l e     a t     x = 1                   L . H . L . = l i m x → 1 − f ( x ) − f ( 1 ) x − 1                                                   = l i m x → 1 − ( x 2 + 1 ) − ( 1 + 1 ) x − 1                                                   = l i m x → 1 − x 2 + 1 − 2 x − 1 = l i m x → 1 − x 2 − 1 x − 1                                                   = l i m x → 1 − ( x − 1 ) ( x + 1 ) x − 1 = l i m x → 1 − ( x + 1 ) = ( 1 + 1 ) = 2                   R . H . L . = l i m x → 1 + f ( x ) − f ( 1 ) x − 1                                                   = l i m x → 1 − ( 3 − x ) − ( 1 + 1 ) x − 1                                                   = l i m x → 1 − ( 3 − x ) − 2 x − 1 = l i m x → 1 − 1 − x x − 1 = − 1 ∴               L . H . L . ≠ R . H . L . S o ,     f ( x )     i s     n o t     d i f f e r e n t i a b l e     a t     x = 1 . H e n c e ,     R o l l e ' s     T h e o r e m     i s     n o t     a p p l i c a b l e     i n     [ 0 , 2 ] .

New answer posted

a year ago

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A
alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Sol:

New question posted

a year ago

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New answer posted

a year ago

0 Follower 5 Views

A
alok kumar singh

Contributor-Level 10

This is a Short Answer Type Questions as classified in NCERT Exemplar

Sol:

G i v e n     t h a t                     f ( x ) = x ( x + 3 ) e − x / 2     i n     [ − 3 , 0 ] (i)  Algebraic  functions  and  exponential  functions  are  continuous  in  their  domains. ∴ f ( x )     i s     c o n t i n u o u s     i n     [ − 3 , 0 ] . ( i i )               f ' ( x ) = x ( x + 3 ) . d d x e − x / 2 + x . e − x / 2 . d d x ( x + 3 ) + ( x + 3 ) . e − x / 2 d d x . x                                                       = x ( x + 3 ) . e − x / 2 . ( − 1 2 ) + x . e − x / 2 . 1 + ( x + 3 ) . e − x / 2 . 1                                                       = e − x / 2 [ − x ( x + 3 ) 2 + x + x + 3 ]                                                       = e − x / 2 [ − x ( x + 3 ) 2 + 2 x + 3 ] = e − x / 2 [ − x 2 − 3 x + 4 x + 6 2 ]                                                       = e − x / 2 [ − x 2 + x + 6 2 ]     w h i c h     e x i s t s     i n     ( − 3 , 0 ) S o     f ( x )     i s     d i f f e r e n t i a b l e     i n     ( − 3 , 0 ) . ( i i i )               f ( − 3 ) = ( − 3 ) ( − 3 + 3 ) e − 3 / 2     = 0                                       f ( 0 ) = ( 0 ) ( 0 + 3 ) e − 0 / 2     = 0 ∴                           f ( − 3 ) = f ( 0 ) = 0 As  the  above  conditions  are  satisfied,  then  there  must  exist  at  least  one  point c∈(−3,0)  such  that  f'(c)=0 ∴     e − c / 2 [ − c 2 + c + 6 2 ] = 0                 ⇒ − e − c / 2 2 [ ( c − 3 ) ( c + 2 ) ] = 0                 ⇒ − e − c / 2 ≠ 0 ∴           ( c − 3 ) ( c + 2 ) = 0 ⇒       c = 3 , − 2                   c = 3 , − 2 ∈ ( − 3 , 0 ) H e n c e ,     R o l l e ' s     T h e o r e m     i s     v e r i f i e d .

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