# differentiationWatch

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#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
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
5 years ago
#3
(Original post by mrdetermination)
...
The answer in the book is correct.

0
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).
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#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
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5 years ago
#6
D^2y/dx^2 = 30x
30 times 2 = 60

Posted from TSR Mobile
0
#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
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
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
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
0
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