What am i doing wrong? Log differentiation

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A_Munk3y
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Homework Statement


Use logarithmic differentiation to find the derivative of the function.
y=xln(x)


also, if anyone could help me with this...
i have (for a diff problem) 1/(x2-1)1/2 * 1/2(x2-1)-1/2*2x
i know that is right, but i don't know how to get from that, to x/(x2-1)
i keep getting x/(x2-1)-1 because i thought that (x2-1)-1/2/(x2-1)1/2 = (x2-1)-1

The Attempt at a Solution



=> ln(y)=ln(xln(x))
=> ln(y)=ln(x)*ln(x)
1/y*y'=1/x*ln(x)+1/x*ln(x)
y'=1/x*ln(x)+1/x*ln(x)*xln(x)
 
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A_Munk3y said:
=> ln(y)=ln(xln(x))
=> ln(y)=ln(x)*ln(x)
1/y*y'=1/x*ln(x)+1/x*ln(x)
y'=1/x*ln(x)+1/x*ln(x)*xln(x)

Looks like you have a typo there with missing parentheses.

y'=(1/x*ln(x)+1/x*ln(x))*xln(x)

or y'=2*ln(x)*xln(x)-1
 
yea, i see the typo. Thanks for pointing that out, but

how did you get from the first equation to the 2nd?
where did the 1/x's go and how did you get xln(x)-1
 
A_Munk3y said:
how did you get from the first equation to the 2nd?
where did the 1/x's go and how did you get xln(x)-1

Oh, that is because 1/x=x-1 and then generally, xa*xb=xa+b.
 
Ahh! i see :)
Alright thanks for the help man!
I really appreciate it