differentiation Watch

mrdetermination
Badges: 3
Rep:
?
#1
Report Thread starter 5 years ago
#1
i was wondering if this correct

q1, find the value of d^2y/dx^2 when x=2 if y=5x^3 + 6x

15x^2 +6

15x=2

x= 2/15

my book says the answer if 60
0
reply
Notnek
Badges: 20
Rep:
?
#2
Report 5 years ago
#2
(Original post by mrdetermination)
i was wondering if this correct

q1, find the value of d^2y/dx^2 when x=2 if y=5x^3 + 6x

15x^2 +6

15x=2

x= 2/15

my book says the answer if 60
I'm not sure where you got 15x=2 from. You need to find d^2y/dx^2 (the second derivative) which is the derivative of 15x^2 +6.

Then plug in x=2 to get the answer.
0
reply
Khallil
Badges: 13
Rep:
?
#3
Report 5 years ago
#3
(Original post by mrdetermination)
...
The answer in the book is correct.

y = 5x^3 + 6x

\Rightarrow \ \dfrac{dy}{dx} = 15x^2 + 6

\Rightarrow \ \dfrac{d^2 y}{dx^2} = \dfrac{d}{dx} \left( \dfrac{dy}{dx} \right) = \ ?
0
reply
Felix Felicis
Badges: 13
Rep:
?
#4
Report 5 years ago
#4
(Original post by mrdetermination)
i was wondering if this correct

q1, find the value of d^2y/dx^2 when x=2 if y=5x^3 + 6x

15x^2 +6
You've only calculated what dy/dx is, you need to differentiate a second time to find d^2y/dx^2.

15x=2

x= 2/15
Not quite sure what you've done here. Differentiate a second time to find an equation for d^2y/dx^2 in terms of x and then find the value of d^2y/dx^2 when x = 2 (i.e. sub in x = 2).
0
reply
mrdetermination
Badges: 3
Rep:
?
#5
Report Thread starter 5 years ago
#5
ow the dude from exam solutions confused and i understand know thanks is he doing it wrong?


http://www.examsolutions.net/maths-r...tutorial-1.php
0
reply
THEMathlete
Badges: 3
Rep:
?
#6
Report 5 years ago
#6
D^2y/dx^2 = 30x
30 times 2 = 60

Posted from TSR Mobile
0
reply
mrdetermination
Badges: 3
Rep:
?
#7
Report Thread starter 5 years ago
#7
one more question is

dy/dx th same as f'(x)

and is d^2y/dx^2 the same sa f''(x)

or are they completely different?
0
reply
THEMathlete
Badges: 3
Rep:
?
#8
Report 5 years ago
#8
(Original post by mrdetermination)
one more question is

dy/dx th same as f'(x)

and is d^2y/dx^2 the same sa f''(x)

or are they completely different?
Yeah they're the same

Posted from TSR Mobile
0
reply
TenOfThem
Badges: 16
Rep:
?
#9
Report 5 years ago
#9
(Original post by mrdetermination)
one more question is

dy/dx th same as f'(x)

and is d^2y/dx^2 the same sa f''(x)

or are they completely different?

dy/dx is the differential of y with respect to x

f'(x) is the differential of f(x) with respect to x
0
reply
Kvothe the Arcane
Badges: 20
Rep:
?
#10
Report 5 years ago
#10
(Original post by mrdetermination)
one more question is

dy/dx th same as f'(x)

and is d^2y/dx^2 the same sa f''(x)

or are they completely different?
Just different notation. if y=f(x), then \dfrac{dy}{dx}=y'=f'(x)
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Manchester Metropolitan University
    Undergraduate Open Day Undergraduate
    Wed, 19 Jun '19
  • University of West London
    Undergraduate Open Day - West London Campus Undergraduate
    Wed, 19 Jun '19
  • University of Warwick
    Undergraduate Open Day Undergraduate
    Fri, 21 Jun '19

How did your AQA A-level Biology Paper 2 go?

Loved the paper - Feeling positive (414)
18.63%
The paper was reasonable (1054)
47.43%
Not feeling great about that exam... (493)
22.19%
It was TERRIBLE (261)
11.75%

Watched Threads

View All