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Find a function \(y=f(x)\) satisfying the given differential equation and the prescribed initial condition. \(\frac{d y}{d x}=\frac{1}{x^{2}} ; y(1)=5\)

Short Answer

Expert verified
The function is \(y = -\frac{1}{x} + 6\).

Step by step solution

01

Identify the Type of Equation

We start by examining the given differential equation \(\frac{d y}{d x} = \frac{1}{x^{2}}\). It is a first-order separable differential equation, where the derivative of \(y\) with respect to \(x\) is given as a function of \(x\) alone. This cues us to separate variables as the first step towards solving the equation.
02

Separate the Variables

Rewrite the differential equation in a form where all terms involving \(y\) are on one side and all terms involving \(x\) are on the other. In this case, the equation can be interpreted as already separated: integrate both sides with respect to \(x\).
03

Integrate Both Sides

Integrate both sides with respect to \(x\):\[y = \int \frac{1}{x^2} \, dx\]The right-hand side integral can be solved using the power rule for integration.
04

Apply the Power Rule for Integration

Compute the integral using the formula \(\int x^{-n} \, dx = \frac{x^{-n+1}}{-n+1} + C\). In our case, \(n = 2\), so:\[y = -\frac{1}{x} + C\]where \(C\) is the constant of integration.
05

Apply the Initial Condition

Use the initial condition \(y(1) = 5\) to find the value of the constant \(C\). Substitute \(x = 1\) and \(y = 5\) into the integrated equation:\[5 = -\frac{1}{1} + C\]Solve for \(C\):\[5 = -1 + C\]\[C = 6\]
06

Write the Final Solution

Substitute the value of \(C\) back into the equation to get the particular solution:\[y = -\frac{1}{x} + 6\]This function satisfies both the differential equation and the initial condition.

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Key Concepts

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

Initial Conditions
In solving differential equations, initial conditions are crucial, as they help to determine the particular solution among a family of solutions. In the given problem, the initial condition is specified as \(y(1) = 5\). This means that when \(x = 1\), the function \(y\) should equal 5. This pinpoints a precise solution on the curve that fits both the differential equation and the specific starting point.Without initial conditions, we can only find a general solution. Initial conditions let us fold in additional real-world constraints or specific requirements. Imagine initial conditions as signposts that guide us to the right path on a maze of possible solutions. In our problem, applying the initial condition means taking the solution after integration and ensuring any constants (unknowns) are adjusted so that \(y(1) = 5\) holds true.
Integration Techniques
When dealing with first-order separable differential equations, integrating both sides of the equation is often required to solve the problem. In this problem, you've got to integrate \( \frac{1}{x^2} \) with respect to \(x\). This involves using the power rule for integration.The Power Rule for Integration
The power rule states that the integral of \( x^{-n} \) is \( \frac{x^{-n+1}}{-n+1} + C \). In our case, \( n = 2 \), so the integral becomes \( -\frac{1}{x} + C \). Here, you simplify the expression \( x^{-2} \) by increasing the exponent by one and dividing by the new exponent, making sure to tack on the constant of integration \( C \) at the end.These integration techniques allow us to transform a differential equation into a direct expression for \( y \), making it manageable to apply the initial conditions and solve for constants.
Constant of Integration
Every time you integrate, a constant of integration \( C \) is added to your solution. In the context of differential equations, this constant reflects the family of solutions generated by indefinite integration.Why is \( C \) Important?
  • When you integrate, you’re finding an antiderivative that fits a wide array of possible functions.
  • The constant \( C \) represents variations in those functions consistent with the differential equation.
To pin down the exact value of \( C \), we use the initial condition, such as \( y(1) = 5 \). With \( y = -\frac{1}{x} + C \), substituting \( x = 1 \) and \( y = 5 \) helps us isolate \( C \) to find \( C = 6 \).The constant, therefore, personalizes the solution to fit the specific scenario laid out by the initial conditions, allowing us to shift from a general solution to one that precisely meets the problem's requirements.

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