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# c3 differentiation question watch

1. If A = y + 1/(y+3), find dA/dy, simplifying the answer.

i got 1-(y+3)

the answer in the back of the book is completely different, its:

(y+2)(y+4) / (y+3)^2

and also:

x= 1/4y^2

i got:

x = 4y^-2
= -8y^-3
but the answers say:
-2y^3
2. The book is right.

You should have 1-1/(y+3)^2
3. (Original post by steve10)
The book is right.

You should have 1-1/(y+3)^2
how?
and you answer isn't what the book says.
4. (Original post by SeekerOfKnowledge)
If A = y + 1/(y+3), find dA/dy, simplifying the answer.

i got 1-(y+3)

the answer in the back of the book is completely different, its:

(y+2)(y+4) / (y+3)^2

I dunno where you got that from...
This is done using the quotient rule:

so u= y+1
v= y+3

can you go on from here...when I did this I got something different to what the book says too:

...not sure if its right ~ I'll check it again.

Edit: ohh wait did I miss read the question..
did you mean
in this case you'd apply the quotient rule to the second part and this could give you the answer which the book has..
5. is it y + 1/(y+3) or (y +1)/(y+3), ????
6. its differentiation ques. not simplifying ,, use quotient rule in chapter 8
7. OP is either reading the wrong questions/ answers, is drunk or is just trolling!!!
8. (Original post by SeekerOfKnowledge)
how?
and you answer isn't what the book says.

dA/dy = 1-1/(y+3)^2

simplify the rhs and you get the book's answer

9. EDIT: I'm an idiot, the chain rule will do:

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