# Thread: Please can anyone help to give the derivative of this beast!

1. ## Please can anyone help to give the derivative of this beast!

f(x)= $x^3 + \frac{3}{2} x^2 - \frac{135}{16} x + \frac{25}{4}$

like in terms of if the question were for f(x)=cosx-x then its derivative would be f'(x) = -sinx-1?

Thanks fo rany help/advise

Steve

2. is it just $f(x) = 3x^2 ?$

3. Originally Posted by maxmadx
f(x)= $x^3 + \frac{3}{2} x^2 - \frac{135}{16} x + \frac{25}{4}$

like in terms of if the question were for f(x)=cosx-x then its derivative would be f'(x) = -sinx-1?

Thanks fo rany help/advise

Steve
It is,
$(x^3)' + \frac{3}{2} (x^2)' - \frac{135}{16}(x)' + \left( \frac{25}{4} \right) '$

4. 3x^2 + 3x - 135/16

5. Originally Posted by Paige05
3x^2 + 3x - 135/16
Yup!

-Dan

6. Hi, can I ask why an online derivative calculator gives:

3x^2 + (3/2)2x-135/16

which is different?

7. Originally Posted by maxmadx
Hi, can I ask why an online derivative calculator gives:

3x^2 + (3/2)2x-135/16

which is different?
That middle term simplifies to what I gave you. I presume the program isn't simplifying the result and if you put a fraction in front of, say the x^3 term, you would see a similar result.

-Dan