## mlddmlnog 2 years ago Calculus help!

1. raxis

Where's the question? ^^;

2. mlddmlnog

The derivative of $f(x)=\frac{ x ^{4} }{ 3 }-\frac{ x ^{5} }{ 5 }$ attains its maximum value at x=?

3. mlddmlnog

4. mlddmlnog

I found the derivative, and set it equal to zero, but 1 was not one of the values i got... :(

5. zepdrix

Ya the answer key is incorrect, it appears to have a max at $$x=\dfrac{4}{3}$$. I keep getting x=3/4 when I work it out though, so I gotta figure out where my mistake is.

6. zepdrix

OH the problem was probably SUPPOSE TO BE,$\large f(x)=\frac{x^4}{\color{salmon}4}-\frac{x^5}{5}$

7. zepdrix

Because that clearly gives a critical point at x=1

8. mlddmlnog

ohh if you do it like that, do you get the right answer? ohh ok :pgoshh these problems :(

9. zepdrix

Oh yah it's x=4/3. I see where my mistake was :O Were you able to get that value?

10. mlddmlnog

yupp :)

11. zepdrix

yah looks like teacher made silly mistake c: that happens