Math Is Fun Forum

Joker

Member

Registered: 2010-04-20

Posts: 51

find derivatives

1) (x² + 2)² ÷ (x² + x-¹)³

2) (x²  + 1)² (x³ - 2x)²

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: find derivatives

Hi Joker;

We can start with 2) first:

We have already covered a lot of this in the previous posts. I showed you the general methods that you need to know. First, have you tried this:

That is the formula for the diff. of a product. Please show me what you have done so far so I can see what you didn't understand from yesterday.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Joker

Member

Registered: 2010-04-20

Posts: 51

Re: find derivatives

hey,
Do i expand the brackets before i differentiate?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: find derivatives

Hi Joker;

If that is the only idea you have then that's okay. Any answer is better than no answer at all. At least you can get partial credit if you try something. Show me what you get and we will go from there.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Joker

Member

Registered: 2010-04-20

Posts: 51

Re: find derivatives

f(x)= (x^2-2)^2        f(g)= (x^3-2x)^2
      = (2x^4-4)               = (2x^5-8x^2)
(2x^4-4)(10x^4-16x) + (2x^5-8x^2)(8x^3)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: find derivatives

Hi Joker;

(x^2 - 2)^2 doesn't equal (2x^4 - 4). Show me how you multiplied it.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Joker

Member

Registered: 2010-04-20

Posts: 51

Re: find derivatives

ooo
how about this?
(x^2-2)(x^2-2)
2x^4-2x^2-2x^2+4
2x^4-4x^2+4

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: find derivatives

Hi Joker;

That is not quite correct either. Try the foil method.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Joker

Member

Registered: 2010-04-20

Posts: 51

Re: find derivatives

x^4-4x^2+4 ? am i getting close?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: find derivatives

Hi Joker;

That is correct! Now if you are determined to expand it before differentiating it then please do that now. Will be back in a little while, going to eat.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Joker

Member

Registered: 2010-04-20

Posts: 51

Re: find derivatives

f(x) = x^4-4x^2+4       g(x) = x^6-4x^3+4x^2
d [f(x)g(x)] = (x^4-4x^2+4)(6x^5-12x^2+8x) + (4x^3-8x)(x^6-4x^3+4x^2)
i think i know what to do now

Joker

Member

Registered: 2010-04-20

Posts: 51

Re: find derivatives

would it be the same way differentaiting the function above as this (3x + 5)^10 function?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: find derivatives

Hi Joker;

Did you get this for your expansion?

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.