Math Is Fun Forum

Gercel

Member

Registered: 2009-07-03

Posts: 16

HELP Find a Derivative of a Square Root Function

What are Derivatives for
1.         Square Root 2x             ????
2.         Square Root 3x             ????
3.          2/Square root x            ????

Please help me state state a derivative for each of them

Also help me  to solve the following Equation using Product/Quotient Rule.
f(x)= 2x^2-3x-1/x^3

Thank you once again.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: HELP Find a Derivative of a Square Root Function

Hi Gercel;

#1

#2

#3

Last edited by bobbym (2009-07-03 10:09:00)

---

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.

Gercel

Member

Registered: 2009-07-03

Posts: 16

Re: HELP Find a Derivative of a Square Root Function

oo thank you
But, can you please explain how you got that?

Thankx)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: HELP Find a Derivative of a Square Root Function

Hi Gercel;

Use power rule on #3.
Please be more specific on what you require on the last problem.

Last edited by bobbym (2009-07-03 11:02:12)

---

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.

Gercel

Member

Registered: 2009-07-03

Posts: 16

Re: HELP Find a Derivative of a Square Root Function

As I understand. for the # 1

You did. 2x^½
             2(½)x^-½
             1x^-½
              ----After that I am not sure what you did?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: HELP Find a Derivative of a Square Root Function

Hi Gercel;

Use chain rule.

Last edited by bobbym (2009-07-03 10:37:02)

---

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.

Gercel

Member

Registered: 2009-07-03

Posts: 16

Re: HELP Find a Derivative of a Square Root Function

Hi bobbym:

But  after (2x)^(1/2) = (1/2)(2x)^(-1/2) all those steps... I get 1x^1/2, How do you put it in the form of 1/√2x ??

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: HELP Find a Derivative of a Square Root Function

Hi Gercel;
Lets start like this: With the chain rule:

say

so:

Last edited by bobbym (2009-07-03 11:11:43)

---

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.

Gercel

Member

Registered: 2009-07-03

Posts: 16

Re: HELP Find a Derivative of a Square Root Function

hmm, what about 2nd question, even though it is almost the same as the First one but you get √3/2√x ... can you please show me step by step how you got it. Please

Thanks)

Last edited by Gercel (2009-07-03 10:44:13)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: HELP Find a Derivative of a Square Root Function

Hi Gercel;

say

so:

Last edited by bobbym (2009-07-03 11:11:25)

---

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.

Gercel

Member

Registered: 2009-07-03

Posts: 16

Re: HELP Find a Derivative of a Square Root Function

If possible do you mind showing how you also got #3???

Thanks ^2

glenn101

Member

Registered: 2008-04-02

Posts: 108

Re: HELP Find a Derivative of a Square Root Function

Hi Gercel, I'll show you how to go about #3.
y=2/√x
this is the same as 2*x^(-1/2)
now simply using your power rule
dy/dx=-1*x^-3/2
=  -1
     -------
      x^3/2
Maybe it's your fraction area that isn't enabling you to get this?
what you have to do is multiply the 2 by -1/2 which gives your -1
and then with your power (-1/2)-(1)=    (-1/2)-(2/2)= -3/2
hence you arrive at your answer.
Hope this helps:)

---

"If your going through hell, keep going."

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: HELP Find a Derivative of a Square Root Function

Hi Gercel;

What do you need done with this function.
f(x)= 2x^2-3x-1/x^3

---

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.

glenn101

Member

Registered: 2008-04-02

Posts: 108

Re: HELP Find a Derivative of a Square Root Function

Hi Gercel and Bobbym,
I believe she wants to know how to evaluate
y=2x^2-3x-1/x^3
Using both the product and quotient rule methods.
I'll show you the quotient rule way;

Ok so we see some terms where we can apply the power rule, oh and by the way this all can be done by using the power rule on each term, anyway as for the quotient.

For the term 1/x^3
Let u =1, v=x^3
     du/dx= 0,   dv/dx= 3x^2.
dy/dx= v(du/dx)-u(dv/dx)
            ---------------------
                        v^2
         = -3x^2
            ----------
                x^6
        =     -3/x^4
and then you just combine that and the other terms using the power rule and you get;
4x-3-3/x^4
there we go, again sorry for that

check by the power rule:
= 4x-3-3/x^4

Last edited by glenn101 (2009-07-03 19:16:13)

---

"If your going through hell, keep going."

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: HELP Find a Derivative of a Square Root Function

Hi glenn101;
There is some mistake with how you are using the quotient rule because (by the power rule)

---

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.

glenn101

Member

Registered: 2008-04-02

Posts: 108

Re: HELP Find a Derivative of a Square Root Function

oh my god, I'm sorry I integrated!
I've been doing integration all day, sorry!

---

"If your going through hell, keep going."

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: HELP Find a Derivative of a Square Root Function

Thats OK

---

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.

Gercel

Member

Registered: 2009-07-03

Posts: 16

Re: HELP Find a Derivative of a Square Root Function

Thanks guys , appreciate your help....
Thanks x 2