To use the chain rule, we'll specify first that f(x) is
the result of composition of 2 functions.
u(x) = x^3 + 4
and v(u) = u^4
f(x) = (vou)(x) = v(u(x)) = v(x^3 + 4) =
(x^3 + 4)^4
We'll differentiate f(x) and we'll
get:
f'(x) =
v'(u(x))*u'(x)
First, we'll differentiate v with respect to
u:
v'(u) = 4u^(4-1) =
4u^3
Second, we'll differentiate u with respect to
x:
u'(x) = (x^3 + 4)' =
3x^2
f'(x) = 4u^3*3x^2
We'll
substitute u and we'll get:
The derivative of
f(x) is: f'(x) = 12x^2*( x^3 + 4)^3.
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