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# differentiation question c3 watch

1. Please could I have some help this question
A= y + 1/ ( y +3), find dA/ dy simplifying the answer
2. 1 -1/(y+3)^2
3. (Original post by Zarantulas)
Please could I have some help this question
A= y + 1/ ( y +3), find dA/ dy simplifying the answer
Use the quotient rule. In this case:

If we say, u=y+1 and v=y+3, differentiate those two equations separately.

Now, multiply u' (the derivative of u) by v and multiply v' by u. Then all you need to do to make it correct when using the quotient rule is have what you've just worked out over v^2.

4. You have used quotient rule, so you differentiate the top and bottom which both should be dy/dx for both. So you should get (2dy/dx)/(y+3)^2
Just check this is right, haven't done this in a while.
5. (Original post by jamestg)
Use the quotient rule. In this case:

If we say, u=y+1 and v=y+3, differentiate those two equations separately.

Now, multiply u' (the derivative of u) by v and multiply v' by u. Then all you need to do to make it correct when using the quotient rule is have what you've just worked out over v^2.

It'd be easier to write as a negative power and use the chain rule.
6. (Original post by NotNotBatman)
It'd be easier to write as a negative power and use the chain rule.
Yep, but I usually want to avoid negative powers just for simplicity and both methods would take about the same time.

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