style
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Just come across this question and have no idea how to even start
dy/dx at point (8,2) on the curve 3y^2 -2y=x
have a total metal block please help!
thanks in advance
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generalebriety
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#2
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Implicit differentiation. Does that mean anything to you?

Alternatively, you could divide by 3, then complete the square on the left hand side and try and rearrange the equation so it's in the form "y = ...".
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Kyalimers
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3y^2 - 2y = x

Spoiler:
Show
\therefore 1 =  6y \frac{dy}{dx} - 2 \frac{dy}{dx}


I have used implicit differentiation.

Re-arrange to get \frac{dy}{dx} = ...
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(Original post by generalebriety)
Implicit differentiation. Does that mean anything to you?
no havnt heard of it...
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leeming
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You sure its,
3y^2 - 2y = x
and not

y = 3x^2 - 2x

^ if not, then make sure you can get in terms of just y

and just remember things such as
x^(1 \div 2) = \sqrt(x)
and do the differentiation from there, using c2 knowledge

f(x) = x^2



f`(x) = 2x^1

^took too long typing, but people saying implicit differentiation, thats c4, or it is for edexel
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yassir
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#6
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\frac{dy}{dx}
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style
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thanks
I got it now,
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forgottenromeo
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implicit differentiation is c4, dy/dx is 1/dx/dy, so try differentiating in terms of y then doing 1 over
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generalebriety
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(Original post by style)
no havnt heard of it...
Ok. Implicit differentiation allows you to differentiate unknown functions of x (like y) with respect to x. It's basically an application of the chain rule; for example, the derivative of 5y^3 is 15y^2 * dy/dx; the derivative of sin y is dy/dx * cos y. Get it?

If so, differentiate that whole equation with respect to x.

Ooh, alternatively, just differentiate with respect to y and take the reciprocal.
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Kyalimers
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Implicit differentiation is Edexcel C3. I would know seeing as I just had the exam with a question about implicit diff on it.
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forgottenromeo
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i did edexcell, the implicit one was on the one on thursday which was c4
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leeming
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(Original post by sohanshah)
Implicit differentiation is Edexcel C3. I would know seeing as I just had the exam with a question about implicit diff on it.
Humm thought it was C3, and C4 was using the parametrics?
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Kyalimers
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Yeah Parametrics are C4 I think.
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forgottenromeo
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parametrics are c4, its why they introduce the implicit. c3 is just the basics as applied to standard trig i think.
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Kyalimers
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I'm sure I've seen differential equations in C3 though
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forgottenromeo
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differential yeah, the implicit isn't introduced till c4, there isn't much new in c4 its mostly applying what you already know.
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Kyalimers
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(Original post by forgottenromeo)
differential yeah, the implicit isn't introduced till c4, there isn't much new in c4 its mostly applying what you already know.
didn't stop me from failing it this summer :p:
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forgottenromeo
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(Original post by sohanshah)
didn't stop me from failing it this summer :p:
:dito:

this years c4 wasn't the worst it could have been, but it wasn't nice.
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