Question #a787b

2 Answers
Oct 22, 2016

#d/dx(log(xe^x)/log(5))=(x+1)/(xlog(5))#

Explanation:

Another way to do this is to simplify at first using the rule #log(AB)=log(A)+log(B)#:

#log(xe^x)/log(5)=(log(x)+log(e^x))/log(5)=(log(x)+x)/log(5)#

Don't forget that #log(5)# is a constant, so we can bring it out when differentiating:

#d/dx((log(x)+x)/log(5))=1/log(5)d/dx(log(x)+x)#

The derivative of #log(x)# is #d/dxlog(x)=1/x#. The derivative of #x# is #1#.

#1/log(5)d/dx(log(x)+x)=1/log(5)(1/x+1)=1/log(5)((1+x)/x)#

Combining this all:

#d/dx(log(xe^x)/log(5))=(x+1)/(xlog(5))#

Oct 22, 2016

#(1+x) / (xln5)#

Explanation:

STEP 1: Rewrite the expression using logarithm rules
If we remember our logarithm rules, we will recall that #log_bx = logx/logb#.
Using the logarithm rule above, we can rewrite #log(xe^x)/log5# as #log_5(xe^x)#.

STEP 2: Differentiate
Recall our differentiation rule for logarithms: #d/dx log_ax=1/(xlna)#

Combining our log derivative rule with the chain rule, we get:
#d/dx log_5(xe^x) = 1/((xe^x)ln5) * d/dx(xe^x)#
To take the derivative of #xe^x# we must remember to apply the product rule:
#1/((xe^x)ln5) * d/dx(xe^x) = 1/((xe^x)ln5) * [1*e^x + x*e^x]#

STEP 3: Simplify
#1/((xe^x)ln5) * [1*e^x + x*e^x]=[e^x + xe^x] / ((xe^x)ln5) = (1+x) / (xln5)#