Derivatives of Constant Multiples

Example:
y = (-7)*(t4 + 2*t - 1)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:

y = -7 (t4 + 2*t - 1)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,

y = -7 (t4 + 2*t - 1)3
we can think of as
y = c f(t)
So the derivative is
y ' = ( c f(t) )'
  = c f '(t)  
  = -7 ((t4 + 2*t - 1)3)'  
and we just need to know the derivative on the right-hand side of the equation. In this case this is
(t4 + 2*t - 1)3 = 3*(t4 + 2*t - 1)2 (4*t3 + 2 - 0) (by the chain rule)
so the finished derivative is
y ' = -7 ( 3*(t4 + 2*t - 1)2 (4*t3 + 2 - 0) )
  = (-21)*(t4 + 2*t - 1)2 (4*t3 + 2)
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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.