Honda-Acura.net

Notices
The Basement Non-Honda/Acura discussion. Content should be tasteful and "primetime" safe.

Calculus question

Thread Tools
 
Old Mar 6, 2009 | 06:16 AM
Share
  #1  
Pete's Avatar
Pete
Thread Starter
Civilian
 
Joined: Jun 2003
Posts: 8,407
Likes: 1
From: Miami Beach. FL
Default Calculus question
Can someone please explain to me how the first derivative of x²(72-4x) is 12x(12-x). I am not sure how to get that answer.
Reply
0
Old Mar 6, 2009 | 06:21 AM
Share
  #2  
jconeab's Avatar
jconeab
got the nuts
 
Joined: May 2006
Posts: 4,939
Likes: 0
From: emerald city
Default
shit pete... been a while since i've done any math. tried solving it and came out with something really different.
no clue
Reply
0
Old Mar 6, 2009 | 06:23 AM
Share
  #3  
Red X's Avatar
Red X
x pǝɹ
 
Joined: Feb 2003
Posts: 6,246
Likes: 1
From: Upstate
Default
Originally Posted by Pete
Can someone please explain to me how the first derivative of x²(72-4x) is 12x(12-x). I am not sure how to get that answer.
take the derivative of the individual pieces.

dy/dx(72x^2 - 4x^3)= dy/dx(72x^2)-dy/dx(4x^3)

=144x - 12x^2 => 12x(12-x)

If you don't want to open up the parenthesis then you can use the rule:

f*g' + g*f' = (fg)'

so:

f= x^2, f'=2x
g=72-4x, g'=-4

you get:

x^2*(-4)+(72-4x)(2x) = 12x(12-x)
Last edited by Red X; Mar 6, 2009 at 06:30 AM.
Reply
0
Old Mar 6, 2009 | 06:35 AM
Share
  #4  
CRAIGHIMSELF's Avatar
CRAIGHIMSELF
Be good
 
Joined: Feb 2004
Posts: 18,842
Likes: 0
From: Sloppy onshore junk.
Default
You have to be kidding ^
Reply
0
Old Mar 6, 2009 | 06:37 AM
Share
  #5  
RicoD's Avatar
RicoD
Pull my finger
 
Joined: Apr 2004
Posts: 41,423
Likes: 0
From: Arizona
Default
Originally Posted by Red X
take the derivative of the individual pieces.

dy/dx(72x^2 - 4x^3)= dy/dx(72x^2)-dy/dx(4x^3)

=144x - 12x^2 => 12x(12-x)

If you don't want to open up the parenthesis then you can use the rule:

f*g' + g*f' = (fg)'

so:

f= x^2, f'=2x
g=72-4x, g'=-4

you get:

x^2*(-4)+(72-4x)(2x) = 12x(12-x)
Originally Posted by CRAIGHIMSELF
You have to be kidding ^

Funny how this makes sense to me
Reply
0
Old Mar 6, 2009 | 06:38 AM
Share
  #6  
Red X's Avatar
Red X
x pǝɹ
 
Joined: Feb 2003
Posts: 6,246
Likes: 1
From: Upstate
Default
Originally Posted by RicoD
Funny how this makes sense to me
you like math too
Reply
0
Old Mar 6, 2009 | 06:41 AM
Share
  #7  
RicoD's Avatar
RicoD
Pull my finger
 
Joined: Apr 2004
Posts: 41,423
Likes: 0
From: Arizona
Default
Originally Posted by Red X
you like math too

its all addition and subtraction in different forms h:
Reply
0
Old Mar 6, 2009 | 06:50 AM
Share
  #8  
LABARINTH's Avatar
LABARINTH
Better Than Canada!
 
Joined: Dec 2002
Posts: 10,821
Likes: 0
From: Baltimore, MD
Default
wow, I am surprised I still remembered how to do this.
Reply
0
Old Mar 6, 2009 | 06:51 AM
Share
  #9  
jconeab's Avatar
jconeab
got the nuts
 
Joined: May 2006
Posts: 4,939
Likes: 0
From: emerald city
Default
that was actually a really good explanation. i remember it now
Reply
0
Old Mar 6, 2009 | 07:05 AM
Share
  #10  
flyromeo3's Avatar
flyromeo3
 
Joined: Jan 2004
Posts: 6,692
Likes: 0
From: Bethlehem PA
Default
Originally Posted by Red X
take the derivative of the individual pieces.

dy/dx(72x^2 - 4x^3)= dy/dx(72x^2)-dy/dx(4x^3)

=144x - 12x^2 => 12x(12-x)

If you don't want to open up the parenthesis then you can use the rule:

f*g' + g*f' = (fg)'

so:

f= x^2, f'=2x
g=72-4x, g'=-4

you get:

x^2*(-4)+(72-4x)(2x) = 12x(12-x)

Im so glad I went through this in college and dont have to do it again!
Reply
0



Advanced Search
Reply Closed Thread Share
Forum Jump

All times are GMT -8. The time now is 02:44 AM.