# Thread: Find Derivative of this function

1. i have to use log(a) instead of ln(a),

How does this change the question?

2. ok nevermind, i just had to change the notation. I got the question completely right... apparently i dont understand the chain rule and how to use it..

Any idea on the other questions?

3. Originally Posted by dunbeacrab
ok nevermind, i just had to change the notation. I got the question completely right... apparently i dont understand the chain rule and how to use it..

Any idea on the other questions?
Chain rule:

(d/dx)[f(g(x))] = f'(g(x))*g'(x)

4. yeah i just went back into the text and figured it out.

what about the x^4/5-x^9/5 one...

Did u notice which one of the 4 i listed it would be?

5. Originally Posted by dunbeacrab
1/9*(9-5*x)*x^(-1/9)

(9-4*x)*x^(-1/9)

1/5*(4-9*x)*x^(-1/5)

1/4*(5-9*x)*x^(-1/5)

one of these....
take out (1/5)*{x^(-1/5)} common
from f'(x) = (4/5)x^(-1/5) - (9/5)x^(4/5) to get

(1/5)*(4-9*x)*x^(-1/5)

6. thanks everyone, i finally finished them all..just in time.

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