## anonymous 4 years ago Let f(x) = x^(4/3) - 7 x^(-8/3) f '(x) = A xB + C xD, where I think they want me to find a,b,c & d

1. anonymous

I think I use the power rule

2. TuringTest

exactly, and what dd you get?

3. anonymous

f(x)= rx^r-1

4. anonymous

and I get ...

5. anonymous

4/3x^1/3- -56/3x^-3/2 is that right?

6. TuringTest

first term is right, but not the second what is$-\frac83-1$?

7. anonymous

-7/3

8. TuringTest

$-\frac83-1=-\frac83-\frac33=-\frac{11}3$which is your exponent on the second term

9. anonymous

so 4/3x^1/3- -56x^-11/3

10. TuringTest

negative times negative is positive we never write -- and you forgot to divide 56/3 in your final answer

11. anonymous

oh yeah thanks didnt see that

12. anonymous

wait something is wrong 56x^11/3

13. anonymous

i mean 56x^-11/3

14. TuringTest

(56/3)x^(-11/3)

15. anonymous

man I need to be careful

16. TuringTest

-7x^(-8/3) -7(-8/3)x^(-8/3-1) 56/3x^(-11/3) yeah, algebra can get you if you're not paying attention :P