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# differentiation question Watch

1. differentiate with respect to t: (β/(β-t))^α

I get
α*β^α / (β-t)^(α+1)

Is that correct? The method used by the textbook is different: they've done (see image) whereas I got the (β-t))^α in the numerator and then used the chain rule
2. (Original post by zomgleh)
differentiate with respect to t: (β/(β-t))^α

I get
α*β^α / (β-t)^(α+1)

Is that correct? The method used by the textbook is different: they've done (see image) whereas I got the (β-t))^α in the numerator and then used the chain rule
They both work out the same, and they're both missing a minus sign.
3. (Original post by ghostwalker)
they're both missing a minus sign.
how come? I was almost sure the textbook solution would be correct?
4. (Original post by zomgleh)
how come? I was almost sure the textbook solution would be correct?
My mistake! Grovel, grovel!

I was confusing the alpha exponent in the numerator, with the one in the denominator.
5. (Original post by ghostwalker)
My mistake! Grovel, grovel!

I was confusing the alpha exponent in the numerator, with the one in the denominator.
haha phew! thanks anyway, you've helped me way too many times, appreciate it!
6. (Original post by ghostwalker)
My mistake! Grovel, grovel!

I was confusing the alpha exponent in the numerator, with the one in the denominator.
Ok so I've done this one before but looking back at it I can't seem to figure it out-- dy/dx of y=(x-y)^3
answer is 3(x-y)^2 / (1+ 3(x-y)^2
7. (Original post by zomgleh)
Ok so I've done this one before but looking back at it I can't seem to figure it out-- dy/dx of y=(x-y)^3
answer is 3(x-y)^2 / (1+ 3(x-y)^2
Treat it with the chain rule. What do you get for your first line of working?
8. (Original post by ghostwalker)
Treat it with the chain rule. What do you get for your first line of working?
I get 3(x-y)^2
9. (Original post by zomgleh)
I get 3(x-y)^2

So, using the chain rule we get

Make sure you understand it, and then just rearrange.
10. (Original post by ghostwalker)

So, using the chain rule we get

Make sure you understand it, and then just rearrange.
got it, you have once again saved the day! voted you for the most helpful member btw, seeing as I probably won't be able to answer any of your doubts :P

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