# Homework Help: Derivative not correct for online hw submission, but is correct

1. Feb 7, 2013

### Torshi

1. The problem statement, all variables and given/known data
Find the d/dx
(x^2+2x+5)^2

2. Relevant equations

Chain rule
3. The attempt at a solution

2(x^2+2x+5)*(2x+2)*2

2. Feb 7, 2013

### Karnage1993

Why did you apply the chain rule again to (2x+2)? You only need to do it once.

It should be:

$2(x^2 + 2x + 5)(2x + 2)$

Think of it this way: $f(x) = x^2$ and $g(x) = x^2 + 2x + 5$.

Then, $D(f \circ g)(x) = Df(g(x))D(g(x))$

Last edited: Feb 7, 2013
3. Feb 7, 2013

### iRaid

You could also just multiply it out and use the power rule.

4. Feb 7, 2013

### Staff: Mentor

Torshi, your title is misleading. The derivative you show is not correct for online submission, AND it is not correct, as Karnage1993 points out.

5. Feb 7, 2013

### Torshi

I didn't mean it to be misleading. My fault. The reason why I said that was because I was at my university math lab and even one of the math instructors said it was correct, but made a tad mistake until I mentioned it. I figured out the answer though.