Chapter 4: Problem 43
Find each integral. $$ \int\left(\frac{3}{x}-5 e^{2 x}+\sqrt{x^{7}}\right) d x, x>0 $$
Short Answer
Expert verified
The integral is \(3\ln|x| - \frac{5}{2}e^{2x} + \frac{2}{9}x^{9/2} + C\).
Step by step solution
01
Separate the Integral
The given integral is a sum of three different functions integrated with respect to \(x\): \(\int \left( \frac{3}{x} - 5e^{2x} + \sqrt{x^7} \right) dx\). We can separate the integral into three distinct parts: \(\int \frac{3}{x} \, dx\), \(- \int 5e^{2x} \, dx\), and \(\int \sqrt{x^7} \, dx\).
02
Integrate \(\int \frac{3}{x} \ dx\)
Recognize that \(\int \frac{3}{x} \, dx\) is a simple logarithmic function. The integral of \(\frac{1}{x}\) is \(\ln|x|\), so \(\int \frac{3}{x} \, dx = 3\ln|x| + C_1\), where \(C_1\) is a constant of integration.
03
Integrate \(- \int 5e^{2x} \ dx\)
We need to integrate the exponential \(5e^{2x}\). Use the substitution \(u = 2x\), with \(du = 2 \, dx\) or \(dx = \frac{1}{2}du\). The integral becomes \(-5 \cdot \frac{1}{2} \int e^u du = -\frac{5}{2}e^{2x} + C_2\).
04
Integrate \(\int \sqrt{x^7} \ dx\)
Convert \(\sqrt{x^7}\) to \(x^{7/2}\). The integral \(\int x^{7/2} \, dx\) can be computed using the power rule: \(\int x^n \, dx = \frac{x^{n+1}}{n+1} + C \), where \(n = \frac{7}{2}\). This gives \(\frac{x^{9/2}}{9/2} = \frac{2}{9}x^{9/2} + C_3\).
05
Combine All Parts Together
Add the results from each integral to get the final answer: \(3\ln|x| - \frac{5}{2}e^{2x} + \frac{2}{9}x^{9/2} + C\), where \(C = C_1 + C_2 + C_3\) is the constant of integration.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Logarithmic Integration
Logarithmic integration is crucial when the integrand involves a term like \(\frac{1}{x}\). This type of function is linked to the natural logarithm function. The integral of \(\frac{1}{x}\) with respect to \(x\) results in \(\ln|x|\). Therefore, if your integrand includes constants such as \(\frac{3}{x}\), like in our exercise, simply multiply this constant with the result.Always remember:
- The absolute value is essential because logarithms of non-positive numbers are undefined in the real number system.
- Add a constant of integration to account for the family of antiderivatives, represented as \(C\).
Exponential Integration
Exponential integration often involves functions that include exponentials such as \(e^{kx}\). These are straightforward yet important for calculus problems. The standard secret weapon here is substitution. For example, consider integrals involving terms like \(5e^{2x}\). The process involves:
- Substitute \(u = 2x\) and find \(du = 2 \, dx\), rearranging gives \(dx = \frac{1}{2} du\).
- The integral then simplifies to \(\frac{1}{2} \int e^{u} du\) and evaluates to \(\frac{1}{2} e^u\).
- Finally, substitute back to get \(\frac{1}{2} e^{2x}\).
Power Rule Integration
The power rule is a fundamental concept in calculus, particularly for polynomial-like expressions. If your integrand is in the form of \(x^n\), where \(n\) is a constant, the power rule applies directly.For example, use the power rule of integration:
- The integral of \(x^n\) with respect to \(x\) is \(\frac{x^{n+1}}{n+1} + C\).
- Consider \(\sqrt{x^7}\) as \(x^{7/2}\). Using the power rule here involves noticing that the power increases by one. So, the integral becomes \(\frac{x^{9/2}}{9/2}\).
- This simplifies quickly to \(\frac{2}{9}x^{9/2}\), remembering to incorporate the constant of integration \(C\).