Hi,

How do I solve for the following: $\displaystyle d/dx [(0.1x + 0.4)log(0.1x + 0.4)]?$

I got the following answer but I think its wrong: $\displaystyle (1/ln2) + 0.1log(0.1x + 0.4).$

Can somebody help?

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- Oct 7th 2009, 07:19 AMlight85Help with simple differentiation
Hi,

How do I solve for the following: $\displaystyle d/dx [(0.1x + 0.4)log(0.1x + 0.4)]?$

I got the following answer but I think its wrong: $\displaystyle (1/ln2) + 0.1log(0.1x + 0.4).$

Can somebody help? - Oct 7th 2009, 07:46 AMCalculus26
http://www.mathhelpforum.com/math-he...e1d8a387-1.gif

what base log are you using ?

at any rate I'll assume log base 2 from your answer

first of all use the product rule:

[.1x+.4] ' log(.1x+.4) + [.1x+.4] [log(.1x+.4)] '

= .1 log(.1x +.4) + {1/ln(2)}(.1x +.4)(.1/(.1x + .4)

= .1 log(.1x +.4) + .1/ln(2) - Oct 7th 2009, 08:06 AMlight85
Yes, its base 2. Thanks.