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Find \(d y / d x\). $$ y=x^{2} \log _{2}(3-2 x) $$

Short Answer

Expert verified
The derivative is \( \frac{dy}{dx} = 2x \log_2(3 - 2x) - \frac{2x^2}{(3 - 2x)\ln(2)} \).

Step by step solution

01

Identify the Differentiation Rule

The function \( y = x^2 \log_2(3 - 2x) \) is a product of two functions, \( x^2 \) and \( \log_2(3 - 2x) \). We'll use the product rule for differentiation, which states that \( (uv)' = u'v + uv' \), where \( u \) and \( v \) are functions of \( x \). Here, \( u = x^2 \) and \( v = \log_2(3 - 2x) \).
02

Differentiate the First Function

Differentiate \( u = x^2 \) with respect to \( x \). The derivative is \( u' = 2x \).
03

Differentiate the Second Function

For \( v = \log_2(3 - 2x) \), use the chain rule and the formula for the derivative of the logarithm base \( a \), which is \( \frac{d}{dx}\log_a(g(x)) = \frac{1}{g(x)\ln(a)}\cdot g'(x) \). Here, \( g(x) = 3 - 2x \) with \( g'(x) = -2 \). So, \( v' = \frac{-2}{(3 - 2x)\ln(2)} \).
04

Apply the Product Rule

Apply the product rule: \[ \frac{dy}{dx} = u'v + uv' \]. Substitute \( u' = 2x \), \( u = x^2 \), \( v = \log_2(3 - 2x) \), and \( v' = \frac{-2}{(3 - 2x)\ln(2)} \). This gives \[ \frac{dy}{dx} = 2x \log_2(3 - 2x) + x^2 \left(\frac{-2}{(3 - 2x)\ln(2)}\right) \].
05

Simplify the Expression

Combine and simplify the expression: \[ \frac{dy}{dx} = 2x \log_2(3 - 2x) - \frac{2x^2}{(3 - 2x)\ln(2)} \].
06

Verification

Check each term in the derived expression to ensure correct application of the derivative rules and coefficients. Double-check algebraic steps for any mistakes.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Product Rule
The product rule is an essential tool in differentiation when dealing with products of two functions. In simple terms, if you have a function that is the product of two separate functions, say \( u(x) \) and \( v(x) \), then the product rule allows you to find the derivative of the entire product \( y(x) = u(x) \cdot v(x) \). The formula to find the derivative using the product rule is:
  • \( (uv)' = u'v + uv' \)
Here, \( u'(x) \) is the derivative of \( u(x) \), and \( v'(x) \) is the derivative of \( v(x) \).

When applying this to our example function \( y = x^2 \log_2(3 - 2x) \), we identify:
  • \( u = x^2 \)
  • \( v = \log_2(3-2x) \)
The next step involves finding the derivative of each part separately before plugging them back into the product rule. This systematic approach helps prevent mistakes and ensures you understand how each part contributes to the whole function's derivative.
Chain Rule
The chain rule is another vital rule in differentiation, used when you encounter composite functions. When a function is composed of another function, the chain rule helps you differentiate them effectively. The general formula for applying the chain rule is:
  • \( \frac{d}{dx}f(g(x)) = f'(g(x)) \cdot g'(x) \)
This means you first differentiate the outer function and then multiply by the derivative of the inner function.

In our exercise, dealing with the function \( v = \log_2(3 - 2x) \), we treat it as a composite function \( \log_2(g(x)) \) where \( g(x) = 3 - 2x \). By the chain rule, we differentiate like this:
  • Find \( g'(x) = -2 \).
  • Use the derivative formula for the logarithmic function which is \( \frac{1}{g(x)\ln(2)} \) to find \( v'(x) \).
Combining these, we get:
  • \( v'(x) = \frac{-2}{(3 - 2x)\ln(2)} \)
Using the chain rule correctly ensures all parts of a composite function are accounted for in differentiation.
Logarithmic Differentiation
Logarithmic differentiation is a powerful technique specifically useful for functions where the base of a logarithm is not A familiar value like e. In such cases, you apply the rules of logarithmic derivatives to simplify the process. The steps involve utilizing the property of logarithms:
  • \( \frac{d}{dx}\log_a(f(x)) = \frac{1}{f(x)\ln(a)} \cdot f'(x) \)
For our function \( \log_2(3 - 2x) \), the base is 2, which requires adjusting from the usual natural base \( e \) (where \( \ln \) is the natural logarithm) to base 2.

Therefore, to differentiate \( v = \log_2(3 - 2x) \), we followed these steps:
  • First, recognize \( f(x) = 3 - 2x \) within the logarithm.
  • Find \( f'(x) = -2 \).
  • Apply the logarithmic differentiation formula to get \( v'(x) = \frac{-2}{(3 - 2x)\ln(2)} \).
This technique efficiently handles the complications arising from non-standard bases in logarithms.

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Most popular questions from this chapter

(a) Find the error in the following calculation: \(\lim _{x \rightarrow 2} \frac{e^{3 x^{2}-12 x+12}}{x^{4}-16}=\lim _{x \rightarrow 2} \frac{(6 x-12) e^{3 x^{2}-12 x+12}}{4 x^{3}}=0\) (b) Find the correct limit.

If the temperature \(T\) of a metal rod of length \(L\) is changed by an amount \(\Delta T\), then the length will change by the amount \(\Delta L=\alpha L \Delta T\), where \(\alpha\) is called the coefficient of linear expansion. For moderate changes in temperature \(\alpha\) is taken as constant. (a) Suppose that a rod \(40 \mathrm{~cm}\) long at \(20^{\circ} \mathrm{C}\) is found to be \(40.006 \mathrm{~cm}\) long when the temperature is raised to \(30^{\circ} \mathrm{C}\). Find \(\alpha\). (b) If an aluminum pole is \(180 \mathrm{~cm}\) long at \(15^{\circ} \mathrm{C}\), how long is the pole if the temperature is raised to \(40^{\circ} \mathrm{C}\) ? [Take \(\left.\alpha=2.3 \times 10^{-5} /{ }^{\circ} \mathrm{C} .\right]\)

Let \(f(x)=x^{2} \sin (1 / x)\). (a) Are the limits \(\lim _{x \rightarrow 0+} f(x)\) and \(\lim _{x \rightarrow 0^{-}} f(x)\) in- determinate forms? (b) Use a graphing utility to generate the graph of \(f\), and use the graph to make conjectures about the limits in part (a).

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One side of a right triangle is known to be \(25 \mathrm{~cm}\) exactly. The angle opposite to this side is measured to be \(60^{\circ}\), with a possible error of \(\pm 0.5^{\circ}\). (a) Use differentials to estimate the errors in the adjacent side and the hypotenuse. (b) Estimate the percentage errors in the adjacent side and hypotenuse.

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