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Posted by gnozahs on Thursday, June 11, 2009 at 4:03am.

Find the derivative of f(x)=[lnx]^4

let z = ln x dz = dx/x dx = x dz then f(z) = z^4 df = 4 z^3 dz = 4 z^3 dx/x df/dx = (4 /x) (ln x)^3

Thank you! I've been stuck on that problem all night.

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