# What is the second derivative of #f(x) = 6lnx - 5/ x^4 #?

##### 1 Answer

Jan 15, 2016

f''(x)

#= - 6/x^2 - 100/x^6 #

#### Explanation:

Begin by writing the function as:

f(x) = 6 lnx -

# 5x^-4 # then f'(x) =

#6.(1/x) + 20x^-5 #

# f'(x) = 6/x + 20x^-5 = 6x^-1 +20x^-5 #

#rArr f''(x) = - 6x^-2 - 100x^-6 = - 6/x^2 - 100/x^6 #