Chapter 4: Problem 53
Find the most general antiderivative or indefinite integral. You may need to try a solution and then adjust your guess. Check your answers by differentiation. $$\int\left(e^{-x}+4^{x}\right) d x$$
Short Answer
Expert verified
The antiderivative is \(-e^{-x} + \frac{1}{\ln 4} \, 4^x + C\).
Step by step solution
01
Identify Components
Identify different functions inside the integral. In this case, we have two functions: \(e^{-x}\) and \(4^{x}\). The integral can be written as \(\int e^{-x} \, dx + \int 4^{x} \, dx\).
02
Integrate \(e^{-x}\)
The antiderivative of \(e^{-x}\) is \(-e^{-x}\) because the derivative of \(-e^{-x}\) is \(-(-e^{-x})) = e^{-x}\).
03
Integrate \(4^x\)
To integrate \(4^x\), recognize that it can be written as \(e^{x \ln 4}\). Its antiderivative is \(\frac{1}{\ln 4} \, e^{x \ln 4} = \frac{1}{\ln 4} \, 4^x\) because when you differentiate \(\frac{1}{\ln 4} \, e^{x \ln 4}\), you use the chain rule to obtain \(4^x\).
04
Combine Results and Add Constant of Integration
Combine the antiderivatives from Steps 2 and 3, and add a constant \(C\). The general form of the antiderivative is \(-e^{-x} + \frac{1}{\ln 4} \, 4^x + C\).
05
Check by Differentiation
Differentiate the result \(-e^{-x} + \frac{1}{\ln 4} \, 4^x + C\). The derivative of \(-e^{-x}\) is \(e^{-x}\) and the derivative of \(\frac{1}{\ln 4} \, 4^x\) is \(4^x\). The constant \(C\) disappears because the derivative of a constant is zero. The result matches the original integrand \(e^{-x} + 4^x\), confirming our solution is correct.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Antiderivative
When dealing with indefinite integrals, we are essentially looking for an antiderivative of a function. An antiderivative is another function that, when differentiated, gives back the original function. In other words, if we have a function \(f(x)\), its antiderivative, often denoted as \(F(x)\), satisfies \(F'(x) = f(x)\). Finding antiderivatives is essential because it allows us to calculate the area under a curve and solve differential equations, among other applications.
- The antiderivative is sometimes known as the indefinite integral.
- Unlike definite integrals, an antiderivative does not have limits of integration and includes a constant of integration \(C\).
- There's usually more than one possible antiderivative due to this constant \(C\).
Exponential Functions
Exponential functions are a fundamental class of functions where the variable is in the exponent. The general form is \(a^x\), where \(a\) is a positive real number. These functions have unique properties, including rapid growth (or decay) and a unique way they integrate and differentiate.
- One of the most common exponential functions is \(e^x\), where \(e\) is the base of natural logarithms.
- The function \(e^{-x}\) is also exponential but represents a decay rather than growth.
- The rules for differentiation and integration rely heavily on the chain rule due to the nature of the exponent.
Chain Rule
The chain rule is a fundamental differentiation technique used when dealing with composite functions. In calculus, the chain rule is familiar for differentiating expressions where one function is nested inside another.
- The chain rule states that if you have a composition of functions \(g(f(x))\), then the derivative is \(g'(f(x)) \cdot f'(x)\).
- This rule is incredibly useful when integrating nested functions, like those involving exponential expressions such as \(e^{f(x)}\).
- Applying it correctly is key to solving many integration problems, especially those that involve changing the base of an exponential function from \(a^x\) to \(e^{x\ln a}\).