Chapter 6: Problem 10
Find the solution of the initial value problem. $$\frac{d y}{d x}=x^{5}+x^{6}, \quad y(1)=2$$
Short Answer
Expert verified
The solution is \( y = \frac{x^6}{6} + \frac{x^7}{7} + \frac{71}{42} \).
Step by step solution
01
Recognize the Form of the Differential Equation
The given differential equation is \( \frac{dy}{dx} = x^5 + x^6 \). This is a straightforward first-order ordinary differential equation where the right side is a polynomial.
02
Integrate Both Sides with Respect to x
To solve \( \frac{dy}{dx} = x^5 + x^6 \), integrate both sides with respect to \( x \). The integral of the left side will just be \( y \), and for the right side, integrate each term separately: \[ \int (x^5 + x^6) \, dx = \int x^5 \, dx + \int x^6 \, dx \].
03
Compute the Integrals
Integrate each term: - \( \int x^5 \, dx = \frac{x^6}{6} + C_1 \)- \( \int x^6 \, dx = \frac{x^7}{7} + C_2 \)Thus, the solution after integration is:\[ y = \frac{x^6}{6} + \frac{x^7}{7} + C \].
04
Apply the Initial Condition to Find C
Use the initial condition \( y(1) = 2 \).Substitute \( x = 1 \) and \( y = 2 \) into the integrated function:\[ 2 = \frac{1^6}{6} + \frac{1^7}{7} + C \].Simplify and solve for \( C \):\[ 2 = \frac{1}{6} + \frac{1}{7} + C \].Calculate \( \frac{1}{6} + \frac{1}{7} = \frac{7}{42} + \frac{6}{42} = \frac{13}{42} \).Thus, \( C = 2 - \frac{13}{42} = \frac{84}{42} - \frac{13}{42} = \frac{71}{42} \).
05
Write the Final Solution
Now substitute \( C \) back into the general solution to get the specific solution satisfying the initial condition:\[ y = \frac{x^6}{6} + \frac{x^7}{7} + \frac{71}{42} \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integration Techniques
Solving first-order ordinary differential equations often requires using integration techniques. In this problem, we are given the differential equation \( \frac{dy}{dx} = x^5 + x^6 \), which we recognize as a polynomial. This identification is crucial because it guides us to integrate each term separately. Here's how we accomplish this:
- First, rewrite the equation in terms of integrals: \( y = \int (x^5 + x^6) \, dx \).
- Separate the integrals: \( \int x^5 \, dx + \int x^6 \, dx \).
- For \( \int x^5 \, dx \), increase the exponent by one and divide: \( \frac{x^6}{6} \).
- Similarly, for \( \int x^6 \, dx \), the result is \( \frac{x^7}{7} \).
Initial Value Problems
Initial value problems involve a differential equation and conditions specified at a particular point. These problems provide not just the form of the solution, but also let us determine specific constants. In our case, the differential equation is \( \frac{dy}{dx} = x^5 + x^6 \). The initial condition given is \( y(1) = 2 \). This condition means that when \( x = 1 \), \( y \) must equal 2.To apply this:
- Substitute \( x = 1 \) into the general solution \( y = \frac{x^6}{6} + \frac{x^7}{7} + C \).
- This gives us the equation: \( 2 = \frac{1^6}{6} + \frac{1^7}{7} + C \).
- Calculate the values: \( \frac{1}{6} + \frac{1}{7} = \frac{13}{42} \).
- Resolve for \( C \): \( C = 2 - \frac{13}{42} = \frac{71}{42} \).
Polynomial Functions
Polynomial functions play a significant role in calculus, especially when dealing with integrations and differential equations. In this problem, the function \( x^5 + x^6 \) is a polynomial. Polynomials are generally in the form of expression consisting of terms with coefficients multiplied by variables raised to a nonnegative integer exponent.Key characteristics of polynomial functions:
- They are continuous and smooth, which means you don't have any breaks or gaps.
- When integrating polynomials, you increase each term's exponent by one and divide by the new exponent.
- Polynomials can be as simple as a linear function or as complex as multi-variable high degree functions.