Chapter 11: Problem 15
Calculate \(\frac{d y}{d x}\) in Exercises 13-20. Simplify your answer. HINT [See Example 5.] \(y=x^{3}\left(1-x^{2}\right)\)
Short Answer
Expert verified
\(\frac{dy}{dx} = 3x^2 - 5x^4\)
Step by step solution
01
Identify the functions
We are given the function:
\[y = x^3(1-x^2)\]
Let's identify the two functions we will be differentiating:
\[f(x) = x^3\]
\[g(x) = 1 - x^2\]
02
Find the derivatives of the functions
Now, we will find the derivatives of both functions with respect to \(x\).
For \(f(x)\):
\[\frac{d}{dx} (x^3) = 3x^2\]
For \(g(x)\):
\[\frac{d}{dx} (1 - x^2) = -2x\]
03
Apply the Product Rule
Now we will use the Product Rule to find the derivative of \(y\) with respect to \(x\):
\[\frac{dy}{dx} = \frac{d}{dx} (f(x)g(x)) = f'(x)g(x) + f(x)g'(x)\]
Plug in the functions and their derivatives we found in steps 1 and 2:
\[\frac{dy}{dx} = (3x^2)(1-x^2) + (x^3)(-2x)\]
04
Simplify the expression
Finally, we will simplify the expression:
\[\frac{dy}{dx} = 3x^2 - 3x^4 - 2x^4\]
Combine like terms:
\[\frac{dy}{dx} = 3x^2 - 5x^4\]
So the simplified derivative of \(y\) with respect to \(x\) is:
\[\frac{dy}{dx} = 3x^2 - 5x^4\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Product Rule
When faced with differentiating a product of two functions, the Product Rule is your best friend. This rule is a key tool in calculus that allows us to find the derivative of two multiplying functions. Imagine this as a way to stitch together the rates of change of both functions to find the overall rate of change for their product. Let's break it down:The Product Rule states that for two functions, say \(f(x)\) and \(g(x)\), the derivative of their product \(f(x)g(x)\) is given by:
- \( (f(x)g(x))' = f'(x)g(x) + f(x)g'(x) \)
- Step 1: Differentiate \(f(x)\) to get \(f'(x)\)
- Step 2: Differentiate \(g(x)\) to get \(g'(x)\)
- Step 3: Use the Product Rule formula to combine them
Derivatives
Derivatives are the cornerstone concept of calculus, representing the rate of change or the slope of a function at any point. When it comes to differentiating basic polynomials, such as \(x^3\) or \(1-x^2\), the process is almost mechanical and very straightforward.### Differentiating Each FunctionGiven a function \(y = x^3(1-x^2)\), we first identify and differentiate each of the component functions:
- For \(f(x) = x^3\), using the power rule, the derivative \(f'(x)\) is \(3x^2\), which comes from multiplying the power by the coefficient and reducing the power by one.
- For \(g(x) = 1 - x^2\), the derivative \(g'(x)\) is \(-2x\). The constant term disappears, and the power rule gives us \(-2x\) as the result.
Simplification of Expressions
After applying calculus techniques like differentiation, you're often left with a somewhat messy expression. Simplification involves cleaning up this expression for better readability and utility.### Combining Like TermsSay you've just applied the Product Rule and ended up with the following expression: \[\frac{dy}{dx} = 3x^2 - 3x^4 - 2x^4\]Here, the term \(-3x^4\) and \(-2x^4\) are like terms — they both contain \(x^4\).### Process of Simplification
- **Identify Like Terms**: In this case, \(-3x^4\) and \(-2x^4\) add up to \(-5x^4\).
- **Combine the Terms**: This yields a more straightforward equation like \(3x^2 - 5x^4\).