Chapter 3: Problem 62
Determine if the derivative rules from this section apply. If they do, find the derivative. If they don't apply, indicate why. $$y=(x+3)^{1 / 2}$$
Short Answer
Expert verified
Derivative rules apply; derivative is \( \frac{1}{2\sqrt{x+3}} \).
Step by step solution
01
Identify the Function Type
The given function is \[ y = (x + 3)^{1/2} \]This is a composite function where the outer function is \(f(u) = u^{1/2}\) and the inner function is \(u = x + 3\).
02
Confirm Applicability of Chain Rule
Since the given function is a composition of functions, and both functions are differentiable, the chain rule can be applied. The chain rule is used to differentiate a composite function \(f(g(x))\).
03
Differentiate the Outer Function
The derivative of the outer function \(f(u) = u^{1/2}\) with respect to \(u\) is \[ f'(u) = \frac{1}{2}u^{-1/2} \].
04
Differentiate the Inner Function
The derivative of the inner function \(u = x + 3\) with respect to \(x\) is \[ \frac{d}{dx}[x + 3] = 1 \].
05
Apply the Chain Rule
Using the chain rule, the derivative of \(y = (x + 3)^{1/2}\) is\[ \frac{dy}{dx} = f'(u) \cdot \frac{du}{dx} = \frac{1}{2}(x+3)^{-1/2} \cdot 1 \].
06
Simplify the Derivative Expression
The simplified form of the derivative is \[ \frac{dy}{dx} = \frac{1}{2\sqrt{x+3}} \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Composite Function
A composite function is essentially a function of a function. It occurs when one function is nested within another. In our example, we have \[ y = (x + 3)^{1/2} \], where the expression involves two functions: an outer function and an inner function.
The outer function is \( f(u) = u^{1/2} \), a square root transformation. Meanwhile, the inner function is \( g(x) = x + 3 \). The composite nature of this function is why you must differentiate with care.
The outer function is \( f(u) = u^{1/2} \), a square root transformation. Meanwhile, the inner function is \( g(x) = x + 3 \). The composite nature of this function is why you must differentiate with care.
- Composite functions often require special rules (like the chain rule) for differentiation.
- Identify the "outer" and "inner" functions to apply the chain rule effectively.
Derivative
The concept of a derivative revolves around the idea of finding the rate at which a function changes with respect to a variable. Simply put, it's a measure of how a function's output changes as the input changes.
For the function \( y = (x + 3)^{1/2} \), we are interested in finding this rate of change with respect to \( x \). To do this, we differentiate the outer function and the inner function:
For the function \( y = (x + 3)^{1/2} \), we are interested in finding this rate of change with respect to \( x \). To do this, we differentiate the outer function and the inner function:
- The derivative of the outer function \( f(u) = u^{1/2} \) with respect to \( u \) is \( f'(u) = \frac{1}{2}u^{-1/2} \).
- For the inner function \( u = x + 3 \), the derivative with respect to \( x \) is simply \( 1 \) since it's a linear function.
Differentiable Functions
To apply concepts like the derivative or the chain rule, the functions involved must be differentiable. A function is differentiable at a point if its derivative exists at that specific point.
In our exercise, both the outer function \( f(u) = u^{1/2} \) and the inner function \( u = x + 3 \) are differentiable. This means:
In our exercise, both the outer function \( f(u) = u^{1/2} \) and the inner function \( u = x + 3 \) are differentiable. This means:
- The derivative of \( f(u) = u^{1/2} \) exists because it's a type of power function, which is differentiable for all its domain.
- The inner linear function \( u = x + 3 \) is differentiable everywhere since linear functions have derivatives that exist everywhere along their graph.