# c3 diffrentiation helpWatch

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Thread starter 11 years ago
#1
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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11 years ago
#2
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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11 years ago
#3

Spoiler:
Show

I have used implicit differentiation.

Re-arrange to get
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Thread starter 11 years ago
#4
(Original post by generalebriety)
Implicit differentiation. Does that mean anything to you?
no havnt heard of it...
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11 years ago
#5
You sure its,

and not

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

and just remember things such as

and do the differentiation from there, using c2 knowledge

^took too long typing, but people saying implicit differentiation, thats c4, or it is for edexel
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11 years ago
#6
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Thread starter 11 years ago
#7
thanks
I got it now,
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11 years ago
#8
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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11 years ago
#9
(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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11 years ago
#10
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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11 years ago
#11
i did edexcell, the implicit one was on the one on thursday which was c4
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11 years ago
#12
(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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11 years ago
#13
Yeah Parametrics are C4 I think.
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11 years ago
#14
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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11 years ago
#15
I'm sure I've seen differential equations in C3 though
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11 years ago
#16
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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11 years ago
#17
(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
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11 years ago
#18
(Original post by sohanshah)
didn't stop me from failing it this summer

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