What am I doing wrong here?
x pǝɹ
Joined: Feb 2003
Posts: 6,246
Likes: 1
From: Upstate
oh holy fuck dont do it that way
y=ln(x^4 + 5x^2)^(3/2)
use ln manip. to get
y=(3/2)(ln(x^4 + 5x^2)
then use the def of deriv of ln to get
y'=(3/2) [(1/(x^4 + 5x^2))(4x^3 + 10x)]
simplify
y'=(12x^3 + 30x)/(2x^4 + 10x^2)
basically y=ln(x)
y'=(dx/x)
but only for lower level stuff, dont do this in 253 or above
y=ln(x^4 + 5x^2)^(3/2)
use ln manip. to get
y=(3/2)(ln(x^4 + 5x^2)
then use the def of deriv of ln to get
y'=(3/2) [(1/(x^4 + 5x^2))(4x^3 + 10x)]
simplify
y'=(12x^3 + 30x)/(2x^4 + 10x^2)
basically y=ln(x)
y'=(dx/x)
but only for lower level stuff, dont do this in 253 or above
Last edited by Red X; Mar 17, 2009 at 03:15 PM.
x pǝɹ
Joined: Feb 2003
Posts: 6,246
Likes: 1
From: Upstate
Member
Joined: Feb 2006
Posts: 1,869
Likes: 0
From: OR
dammit learn your log rules!!!!
anything of the form ln(sdhjfgksdfg)^A can be written as A(ln(sdkfhsdkfghsdfg))
just move the exponent out as a scaler, super useful
look at my first link, there are a few rules you really need to know to do the algebra manipulation to get these types of problems into the proper form for them to be super easy
anything of the form ln(sdhjfgksdfg)^A can be written as A(ln(sdkfhsdkfghsdfg))
just move the exponent out as a scaler, super useful
look at my first link, there are a few rules you really need to know to do the algebra manipulation to get these types of problems into the proper form for them to be super easy
Member
Joined: Feb 2006
Posts: 1,869
Likes: 0
From: OR
bah, nooooooooo
you cant break the ln(a + b) into ln(a) + ln (b) that is not correct!!!!
you are thinking of ln(ab)=ln(a) + ln(b)
multiplication changes to addition, division changes to subtraction
http://www.mathwords.com/l/logarithm_rules.htm
for all rules
wait, thats not even quite what you are doing
whatever it is, line 2 is not correct from line 1
you cant split the ln(a+b) into anything else its in its basic form
you cant break the ln(a + b) into ln(a) + ln (b) that is not correct!!!!
you are thinking of ln(ab)=ln(a) + ln(b)
multiplication changes to addition, division changes to subtraction
http://www.mathwords.com/l/logarithm_rules.htm
for all rules
wait, thats not even quite what you are doing
whatever it is, line 2 is not correct from line 1
you cant split the ln(a+b) into anything else its in its basic form
Last edited by cpvdh; Mar 17, 2009 at 03:50 PM.