# Homework Help: Need Help with a Derivative

1. Sep 25, 2009

### soccerboy2209

Need Help with a Derivative!!

1. The problem statement, all variables and given/known data
{6x+[8x^(1/2)]}^(1/2)

2. Relevant equations

I know its chain rule with a square root inside a square root but i can not seem to get the right answer to enter into the computer program my college uses

3. The attempt at a solution

2. Sep 25, 2009

### Bohrok

Re: Need Help with a Derivative!!

So you want help to rewrite it in a way that will work in the program?
Try entering it with just parentheses ().

3. Sep 25, 2009

### soccerboy2209

Re: Need Help with a Derivative!!

No i can not seem to get the solution

4. Sep 25, 2009

### soccerboy2209

Re: Need Help with a Derivative!!

The square root inside a square root is throwing me off

5. Sep 25, 2009

### Bohrok

Re: Need Help with a Derivative!!

Is this what it looks like?

$$\sqrt{6x + 8\sqrt{x}}$$

6. Sep 25, 2009

### soccerboy2209

Re: Need Help with a Derivative!!

no the 8 is also inside the inner square root

7. Sep 25, 2009

### Bohrok

Re: Need Help with a Derivative!!

You didn't use parentheses correctly, then. 8x needs to be in parentheses.

{6x+[(8x)^(1/2)]}^(1/2)

8. Sep 25, 2009

### soccerboy2209

Re: Need Help with a Derivative!!

Ok but that is the problem and i need the solution

9. Sep 25, 2009

### Bohrok

Re: Need Help with a Derivative!!

How are you entering it into the program?

10. Sep 25, 2009

### soccerboy2209

Re: Need Help with a Derivative!!

(1/2){[6+(8x)^(1/2)]^(-1/2)}{6+(4x)^(-1/2)]

11. Sep 25, 2009

### Bohrok

Re: Need Help with a Derivative!!

Have you tried with just parentheses () and no square brackets [] or curly braces {} ?

12. Sep 25, 2009

### soccerboy2209

Re: Need Help with a Derivative!!

yes but this provides me with the answer i have worked out which is (1/2){6+(8x)^(1/2)]^(-1/2)}[6+(1/2)(8x)^(-1/2)](1/2)[(8x)^(-1/2)](8) and the hint says "You start
with (6x+(8x)^.5))^.5. The inside is (6x+(8x)^.5). So, use the chain
rule on that. Once you have that and have to take the derivative of the
inside, then you need to also do the chain rule with the inside of 8x."

13. Sep 25, 2009

### Bohrok

Re: Need Help with a Derivative!!

So you're having trouble doing it by hand on paper?

14. Sep 25, 2009

### soccerboy2209

Re: Need Help with a Derivative!!

i guess..if my answer doesnt look right, but i believe i am getting the right answer