Math Question

[EvanPFerguson]

How do you go about getting the derivative for this equation (I don't really care about the right answer as I do how to get the answer)


6 / sq(26-x)

 

[Platypus]

If im not mistaken set it to 0

ex)

6/sqt(26-x)=0

Then multiply each side by 6

ex)

6/sqt(26-x)=0*6
____
6

Then it becomes: sqt(26-x)

This is just an educated guess, I hope this helped, if Im way off, sorry, its late

 

[bozo1]

Ok, after 5 hours at the bar and reading this post, I think what's left of my brain just squirted out of my ears.

 

[nd]

Quotient rule.

(denominator)*(derivative of numerator) - (numerator)*(derivative of denominator) divided by the denominator squared.

Sqrt(26-x)*0 - 6*.5(26-x)^(-.5)*-1
--------------------------------
26-x

Then just simplify.

Edit: This does simplify down to 3(26-x)^(-3/2), which correlates to your second choice

 

[EvanPFerguson]

ya, that's not right

 

[EvanPFerguson]

the answer is one of the following btw:

6/[(26-x)^(3/2)]

3/[(26-x)^(3/2)]

-3/[(26-x)^(3/2)]

-6/[(26-x)^(3/2)]

 

[EvanPFerguson]

dp

 

[Napalm381]

Ummmmmmmmm...sorry CorporateRecreation but you're way off.

To get the derivative of this function you use the "power rule": d/dx (x^n) = n * x^(n-1)

In this case, n is -0.5 (a square root in the denominator). The 6 is outside of the square root so it just stays in front. You end up with 6 * -0.5 * (26-x)^-1.5

Then you need to use the chain rule, because you have a function of x "inside" the square root function. The derivative of 26-x is just -1. So you end up with:

6 * -0.5 * (26-x)^-1.5 *-1 = 3 * (26-x)^-1.5

Edit: this correlates to your second, not third, choice. Sorry.

 

[EvanPFerguson]

thanks yo, though......I still don't get this 100%

boo boo

 

[EvanPFerguson]

checked the answer......actually it's


3/(26-x)^(3/2)

 

[nd]

<< checked the answer......actually it's
3/(26-x)^(3/2) >>

Right, see my post.

 

[Napalm381]

&quot;3 * (26-x)^-1.5&quot; is exactly the same as &quot;3/(26-x)^(3/2)&quot;.

 

[EvanPFerguson]

nap, I think you missed the negative

nd was right, thanks

 

[EvanPFerguson]

ok, so how do I get that -1 again?

derivative of 26-x right? for the chain rule?

 

[tigerbait]

mmmmmmmm... Calculus.



yep, -1 comes from the chain rule

 

[EvanPFerguson]

ok, and the chain rule all you do is keep multiplying the derivatives together like that?

 

[RossGr]

evan note that Napalm has the radical in the denominator, this is equivlent to a negitive exponent in the numerator. The 2 answers are equivlent.

 

[EvanPFerguson]

yes, he was right but he said it was the 3rd answer, not the second


perhaps i worded my replys wrong

 

[EvanPFerguson]

my bad!

 

[nd]

Chain rule by example, in short:
The derivative of 7x^3 is obviously 21x^2. This is the power rule.

What if instead of having &quot;x&quot;, you have some other expression.. like, for example, (2x+1)? How would you find the derivative of 7(2x+1)^3 ?

Use the power rule + chain rule. First, do it the way you normally would with the power rule:

21(2x+1)^2

But it can't be that simple, right? Right. You have to take into account what's inside the expression (in this case, 2x+1). Simply take the derivative of that and multiply it by the previous result.

21(2x+1)^2*2

And that's your answer.

 

[EvanPFerguson]

ah, ok

and what if it was sq(2x+1) ??

[.5(2x+1)^-.5]*2?

 

[RossGr]

You got it. Good expaination ND.

 

[EvanPFerguson]

thanks guys


more q's in the future I'm sure

 

[bozo1]

brain matter
grey brain matter
oozing down my face

 

[nd]

<< ah, ok

and what if it was sq(2x+1) ??

[.5(2x+1)^-.5]*2? >>

Yep.