Math Is Fun Forum

tonyz1949

Member

Registered: 2007-08-04

Posts: 20

Derivatives

Let g(x) = f(x² + 1)    Find

a)  g'(x)

b)  g'(2)

c)  g'(x³)

d)  d/dx [g(x³)]

tonyz1949

Member

Registered: 2007-08-04

Posts: 20

Re: Derivatives

Thanks in advance for helping me out. I have an exam. Pleez help me

bossk171

Member

Registered: 2007-07-16

Posts: 305

Re: Derivatives

Here's some tips (not answers though, I'm a little to lazy right now).

a) Try using the chain rule.

b) Using the answer you found in (a), simply substitute 2 for x

c) Try Using the Chain Rule twice. Try re-writing it, that might help you see it better.

d) Just (c) in disguise.

I hope these weren't to cryptic. Post what you came up with so someone smart (like Ricky or JaineFairfax) can give you more (better?) pointers.

---

There are 10 types of people in the world, those who understand binary, those who don't, and those who can use induction.

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

Re: Derivatives

As i said in one of your other posts. Ask for help, dont ask for us to solve your problems. Anyways, im going to solve (a) and tell you how to solve the others like bossk171 did.

Let g(x) = f(x² + 1)   

g'(x) = f'(x^2 + 1)(2x)
        = 2xf'(x^2 + 1)

You cannot give a final answer without knowing the function f which you didnt specify. g(x) is a composite function of f and x^2 + 1

Now for part b, Just substitute 2 for x.

For part c substitute x^3 for x.

Etc