# Easy derivative Q need help

1. Nov 6, 2008

### amac1212

1. The problem statement, all variables and given/known data

- 8 - sqr(29-4x+x^2)

2. Relevant equations

3. The attempt at a solution

-8(-1/2)=4

4(29-4x+x^2)^-1/2(2x-4)???

am i on the right track?

2. Nov 6, 2008

### yoleven

I'm no expert,
if you have sqrt(u) you get 1/2sqrt(u)
I don't think you can do the chain rule because you have -8-sqrt(u),
so I think you have to take the derivative of -8 which is 0 - the derivative of sqrt(u).

3. Nov 6, 2008

### bowma166

Remember that you can split up $$\frac{d}{dx}\left(-8-\sqrt{x^{2}-4x+29}\right)$$ to get $$\frac{d}{dx}\left(-8\right)-\frac{d}{dx}\left(\sqrt{x^{2}-4x+29}\right)$$. From there you can apply the chain rule.

4. Nov 7, 2008

### HallsofIvy

Staff Emeritus
You seem to have thought the -8 was MULTIPLYING the square root- it is not!