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Evaluate the definite integrals. \(\int_{1}^{4}\left(\frac{3}{\sqrt{x}}-\frac{6}{\sqrt{x}}\right) d x\)

Short Answer

Expert verified
The value of the integral is -6.

Step by step solution

01

Simplify the Expression Inside the Integral

Combine the terms inside the integral by subtracting the second term from the first: \[ \int_{1}^{4} \left( \frac{3}{\sqrt{x}} - \frac{6}{\sqrt{x}} \right) \, dx = \int_{1}^{4} \frac{3 - 6}{\sqrt{x}} \, dx = \int_{1}^{4} \frac{-3}{\sqrt{x}} \, dx \]
02

Rewrite the Integrand using Exponents

Rewrite \( \frac{1}{\sqrt{x}} \) as \( x^{-1/2} \). Thus, the integral becomes: \[ \int_{1}^{4} -3x^{-1/2} \, dx \]
03

Integrate the Expression

Apply the power rule for integration, which states \( \int x^n \, dx = \frac{x^{n+1}}{n+1} + C \), to the integral: \[ \int -3x^{-1/2} \, dx = -3 \cdot \frac{x^{1/2}}{1/2} = -6x^{1/2} \]
04

Evaluate the Integral from 1 to 4

Substitute the upper limit and lower limit into the integrated function:\[ \left[-6x^{1/2}\right]_{1}^{4} = [-6(4)^{1/2}] - [-6(1)^{1/2}] = [-6 \times 2] - [-6 \times 1] = -12 + 6 = -6 \]
05

State the Final Answer

The value of the definite integral is \(-6\).

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Key Concepts

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

Integral Calculus
Integral calculus is a core component of mathematical analysis dealing with accumulation of quantities and areas under curves. When we refer to integrals, we often mean finding the total accumulation of a quantity over a certain interval. In our exercise, we're focused on the concept of definite integrals, which help us determine the value of the function in a specific interval, in this case from 1 to 4.
Integrals can be visualized as the sum of infinitesimally small quantities. In essence, the definite integral of a function between two points a and b, noted as \(\int_{a}^{b} f(x) \, dx\), represents the net area between the function and the x-axis for this interval. A positive area is above the x-axis, while a negative area is below it.
Here's what happens in our exercise:- The expression inside the integral, \(\frac{3}{\sqrt{x}} - \frac{6}{\sqrt{x}}\), first needs simplification.- This simplifies the calculation and makes it easier to apply integration techniques later on.
Power Rule for Integration
The power rule is a fundamental principle used to integrate functions of the form \(x^n\). It states that the integral of \(x^n\) is \(\frac{x^{n+1}}{n+1} + C\), where \(C\) is the constant of integration for indefinite integrals. For definite integrals, this simplifies the function without requiring the constant.
When we encounter expressions involving powers, like \(x^{-1/2}\) from our exercise, the power rule becomes particularly handy. In the problem, after simplifying, we rewrite the expression \(\frac{-3}{\sqrt{x}}\) as \(-3x^{-1/2}\). This step prepares the function for the application of the power rule:
  • Increase the power by 1, making \(-1/2 + 1 = 1/2\).
  • Divide by the new power \(1/2\) and multiply by the coefficient \(-3\), yielding \(-6x^{1/2}\).
By using this power rule, we solve the integral easily without complications.
Simplifying Expressions in Integrals
Simplifying expressions is a crucial step in solving integrals efficiently. It allows us to transform complex functions into a form more suitable for integration. In our exercise, simplifying the expression inside the integral reduced \(\frac{3}{\sqrt{x}} - \frac{6}{\sqrt{x}}\) to \(\frac{-3}{\sqrt{x}}\), making the integral much more manageable to evaluate.
Here are the key steps we took during simplification:
  • Identify and factor out common terms or expressions.
  • Rewrite complex fractions using exponents; for example, converting \(\frac{1}{\sqrt{x}}\) to \(x^{-1/2}\).
This simplification is essential, not only for aiding in applying the power rule but also for ensuring a smooth and less error-prone calculation in further steps. In practical scenarios, simplification reduces the likelihood of mistakes in algebraic manipulations and leads to a clearer, more concise solution path.

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