What is the Derivative of g(x) at x=0 if g(x) = [f(x)]^2?

In summary: Here u=f(x) so du/dx= f'(x).In summary, the problem states that if f is differentiable at x=0 and g(x) = [f(x)]^2, with f(0) = f'(0) = -1, then g'(0) = 1. This can be determined by using the chain rule, where g'(x) = 2f(x)f'(x). By plugging in the known values, we get g'(0) = 2(-1)(-1) = 2, which is equivalent to answer choice E.
  • #1
lelandsthename
12
0

Homework Statement


If f is differentiable at x=0 and g(x) = [f(x)]^2, f(0) = f'(0) = -1, then g'(0) =


Homework Equations


MC Answers:
(A) -2 (B) -1 (C) 1 (D) 4 (E) 2


The Attempt at a Solution



The only thing I could think of was that if g(x) = (f(x))^2 then g'(0) = (f'(0))^2 and then g'(0) = 1. Does this make sense? I kind of feel like my logic is pseudo math and is giving me an incorrect answer.
 
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  • #2
I would say C) but I can't say if my thinking is correct...it amounts to the same as yours...except for one part
 
  • #3
By the chain rule, g'(x) = 2f(x)f'(x).
 
  • #4
lelandsthename said:

Homework Statement


If f is differentiable at x=0 and g(x) = [f(x)]^2, f(0) = f'(0) = -1, then g'(0) =


Homework Equations


MC Answers:
(A) -2 (B) -1 (C) 1 (D) 4 (E) 2


The Attempt at a Solution



The only thing I could think of was that if g(x) = (f(x))^2 then g'(0) = (f'(0))^2 and then g'(0) = 1. Does this make sense? I kind of feel like my logic is pseudo math and is giving me an incorrect answer.
You are right- your logic is pseudo math! :smile:The difficulty is that g'(x) is NOT (f'(x))2. As Avodyne said, you need to use the chain rule: g(x)= u2 and u= f(x). dg/dx= (dg/du)(du/dx).
 

Related to What is the Derivative of g(x) at x=0 if g(x) = [f(x)]^2?

1. What is a differentiable function?

A differentiable function is a mathematical function that is smooth and continuous, meaning that it has no abrupt changes or breaks. It is a function that can be represented by a smooth curve and has a well-defined derivative at every point.

2. How is differentiability related to continuity?

Differentiability and continuity are closely related concepts. A function is differentiable at a point if it is continuous at that point and has a well-defined derivative. In other words, a function must be continuous in order to be differentiable.

3. What is the significance of differentiable functions in calculus?

Differentiable functions play a crucial role in calculus as they allow us to find the slope or rate of change of a function at any given point. This is important in many real-world applications, such as optimization problems and physics equations.

4. How can I determine if a function is differentiable?

A function is differentiable if it is continuous and has a well-defined derivative at every point within its domain. This can be determined by checking for any discontinuities or sharp turns in the graph of the function.

5. What are the rules for differentiating a function?

There are several rules for differentiating a function, including the power rule, product rule, quotient rule, and chain rule. These rules allow us to find the derivative of more complex functions by breaking them down into smaller, simpler parts.

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