• Support PF! Buy your school textbooks, materials and every day products Here!

Natural log derivative problem

  • #1
Hello all. I am stuck on this homework problem. It wants me to find
[tex]
\frac {d^2y} {dx^2}
[/tex]
when [tex] y= ln x^8 [/tex]
The book answer is [tex] \frac {-8}{x^2}[/tex]
But I only can get [tex] \frac {-8}{x^9)}[/tex]

Please give me some guidance
Thanks
 
Last edited:

Answers and Replies

  • #2
saltydog
Science Advisor
Homework Helper
1,582
2
compute_a_nerd said:
Hello all. I am stuck on this homework problem. It wants me to find
[tex]
\frac {d^2y} {dx^2}
[/tex]
when [tex] y= ln x^8 [/tex]
The book answer is [tex] \frac {-8}{x^2}[/tex]
But I only can get [tex] \frac {-8}{x^9)}[/tex]

Please give me some guidance
Thanks
Need to keep very clear the precedence of operators so write it as:

[tex]y=ln(x^8)[/tex]

Now, just differentiate once to get 8/x, one more time to get the book's answer.
 
  • #3
Thx so much
 

Related Threads for: Natural log derivative problem

  • Last Post
Replies
24
Views
4K
  • Last Post
Replies
17
Views
2K
  • Last Post
Replies
15
Views
2K
Replies
1
Views
1K
  • Last Post
Replies
2
Views
1K
Replies
8
Views
3K
  • Last Post
Replies
6
Views
15K
  • Last Post
Replies
6
Views
7K
Top