Implicit differentiation help where help stated Watch

REASON_Lighters
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linQ - https://twitter.com/natekeegan1986/s...976704/photo/1

TY -N

Why does the 'x' disappear?
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Kvothe the Arcane
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(Original post by REASON_Lighters)
linQ - https://twitter.com/natekeegan1986/s...976704/photo/1

TY -N

Why does the 'x' disappear?
lna is a number, let's call it c.
\dfrac{d}{dx}cx=c.
Remember x=x^{1} and \dfrac{d}{dx}{x^n}=nx^{n-1} so \dfrac{d}{dx}x^1=1x^{1-1}=1x^0=1^2=1.
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REASON_Lighters
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(Original post by keromedic)
lna is a number, let's call it c.
\dfrac{d}{dx}cx=c.
Remember x=x^{1} and \dfrac{d}{dx}{x^n}=nx^{n-1} so \dfrac{d}{dx}x^1=1x^{1-1}=1x^0=1^2=1.
of course differentiating x gets 1 ffs. Thank you extremely clear layout and work, kind regards.

Thanks makes sense in the end ))))))
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Kvothe the Arcane
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(Original post by REASON_Lighters)
of course differentiating x gets 1 ffs. Thank you extremely clear layout and work, kind regards.

Thanks makes sense in the end ))))))
Don't mention it. Quite often it's these things that cost us the marks
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REASON_Lighters
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(Original post by keromedic)
Don't mention it. Quite often it's these things that cost us the marks
idd :P

I take it you're doing A2 Maths atm, do you do FM as well?
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Kvothe the Arcane
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(Original post by REASON_Lighters)
idd :P

I take it you're doing A2 Maths atm, do you do FM as well?
I did A2 Mathematics last year. Presently, I'm studying AS/A2 Further Mathematics.
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REASON_Lighters
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(Original post by keromedic)
I did A2 Mathematics last year. Presently, I'm studying AS/A2 Further Mathematics.
Very good, me too except I am doing a2 maths this year as well :_)

Sorry to trouble you but I have another question:

R=200(0.9)^t Find the value of dR/dt when t=8

I get dR to be =(200*0.9^t)

But I dont get why you have to multiply by ln 0.9 with my dR
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Kvothe the Arcane
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(Original post by REASON_Lighters)
Very good, me too except I am doing a2 maths this year as well :_)

Sorry to trouble you but I have another question:

R=200(0.9)^t Find the value of dR/dt when t=8

I get dR to be =(200*0.9^t)

But I dont get why you have to multiply by ln 0.9 with my dR
I'm happy to help but do you mind latexing or scanning your question and attempted working?
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REASON_Lighters
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(Original post by keromedic)
I'm happy to help but do you mind latexing or scanning your question and attempted working?
yeah sure sorry:


linQ - https://twitter.com/natekeegan1986/s...305344/photo/1

Well the question is short - and involves product rule, its just that I don't get the 'In 0.9' from the product rule.
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Kvothe the Arcane
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(Original post by REASON_Lighters)
yeah sure sorry:


linQ - https://twitter.com/natekeegan1986/s...305344/photo/1

Well the question is short - and involves product rule, its just that I don't get the 'In 0.9' from the product rule.
Sorry about the late response. Just checking it now, had to do something.
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REASON_Lighters
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(Original post by keromedic)
Sorry about the late response. Just checking it now, had to do something.
No problem, happy for the assistance
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Kvothe the Arcane
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(Original post by REASON_Lighters)
yeah sure sorry:


linQ - https://twitter.com/natekeegan1986/s...305344/photo/1

Well the question is short - and involves product rule, its just that I don't get the 'In 0.9' from the product rule.
I'm not sure I understand your question. You've learnt that \dfrac{d}{dx}a^x=a^xlna. a in this case is 0.9. What's the problem?
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REASON_Lighters
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(Original post by keromedic)
I'm not sure I understand your question. You've learnt that \dfrac{d}{dx}a^x=a^xlna. a in this case is 0.9. What's the problem?
Thank you, yeah that makes sense, so do you have to multiply by 200 with respect to the product rule as well then?
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Kvothe the Arcane
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(Original post by REASON_Lighters)
Thank you, yeah that makes sense, so do you have to multiply by 200 with respect to the product rule as well then?
200 is a constant so it isn't involved in differentiation. It's not a product rule thing, no.
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brianeverit
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(Original post by REASON_Lighters)
linQ - https://twitter.com/natekeegan1986/s...976704/photo/1

TY -N

Why does the 'x' disappear?
Because \frac{dy}{dx} has been omitted, it should be \frac{1}{y}\frac{dy}{dx} om the left hand side.
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Kvothe the Arcane
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(Original post by brianeverit)
Because \frac{dy}{dx} has been omitted, it should be \frac{1}{y}\frac{dy}{dx} om the left hand side.
Ah yes, I hadn't spotted the missing [ted]\dfrac{dy}{dx}[/tex]. Why/how is that the reason?
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