Derivatives of Constant Multiples

Example:
W = 4*(ln(x))3

The first thing to notice when finding the derivative of this function is that it is the product of a constant and another function, as shown in color below:

W = 4 (ln(x))3

The Derivative Rule for Constant Multiples:

The derivative of a constant multiple is the constant times thederivative of the function.
If
  z = c ( f(x) )
then the derivative of z is
  z' = ( c f(x) )'
    = c f '(x)

So our example,

W = 4 (ln(x))3
we can think of as
W = c f(x)
So the derivative is
W ' = ( c f(x) )'
  = c f '(x)  
  = 4 ((ln(x))3)'  
and we just need to know the derivative on the right-hand side of the equation. In this case this is
(ln(x))3 = 3*(ln(x))2 x-1 (by the chain rule)
so the finished derivative is
W ' = 4 ( 3*(ln(x))2 x-1 )
  = 12*x-1 (ln(x))2
[]


additional explanation for the derivative of constant multiples
see another derivative of constant multiples example
practice gateway test
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Comments to Gavin LaRose
glarose@umich.edu
©2001 Gavin LaRose, University of Michigan Math Dept.