Math Problem Statement

Can you do the same problem but dy/dx = 2x-y when y=0 and x= 1

Solution

The differential equation is dydx=2xy\frac{dy}{dx} = 2x - y with the initial condition y(1)=0y(1) = 0. Let's solve this first-order linear differential equation.

Step 1: Rearrange the equation

We can rewrite the equation as: dydx+y=2x\frac{dy}{dx} + y = 2x

This is now a first-order linear equation in the form dydx+P(x)y=Q(x)\frac{dy}{dx} + P(x)y = Q(x), where P(x)=1P(x) = 1 and Q(x)=2xQ(x) = 2x.

Step 2: Find the integrating factor

The integrating factor μ(x)\mu(x) is given by: μ(x)=eP(x)dx=e1dx=ex\mu(x) = e^{\int P(x)\, dx} = e^{\int 1\, dx} = e^x

Step 3: Multiply the equation by the integrating factor

Now, multiply the entire differential equation by the integrating factor exe^x: exdydx+exy=2xexe^x \frac{dy}{dx} + e^x y = 2xe^x This simplifies to: ddx(exy)=2xex\frac{d}{dx} \left( e^x y \right) = 2xe^x

Step 4: Integrate both sides

Integrating both sides with respect to xx: exy=2xexdxe^x y = \int 2xe^x \, dx

To solve 2xexdx\int 2xe^x \, dx, we use integration by parts, where u=2xu = 2x and dv=exdxdv = e^x dx. Applying the formula udv=uvvdu\int u \, dv = uv - \int v \, du:

  • u=2xu = 2x, so du=2dxdu = 2 \, dx
  • dv=exdxdv = e^x \, dx, so v=exv = e^x

Now, 2xexdx=2xex2exdx=2xex2ex\int 2xe^x \, dx = 2x e^x - \int 2e^x \, dx = 2x e^x - 2e^x

Thus, the equation becomes: exy=2xex2ex+Ce^x y = 2x e^x - 2e^x + C

Step 5: Solve for yy

Now, divide through by exe^x: y=2x2+Cexy = 2x - 2 + Ce^{-x}

Step 6: Apply the initial condition

We are given that y(1)=0y(1) = 0. Substituting x=1x = 1 and y=0y = 0 into the solution: 0=2(1)2+Ce10 = 2(1) - 2 + Ce^{-1} 0=22+Ce1=Ce10 = 2 - 2 + Ce^{-1} = Ce^{-1} Thus, C=0C = 0.

Final solution:

Therefore, the solution to the differential equation is: y=2x2y = 2x - 2

Would you like further clarification or details on any step?


Here are 5 related questions to expand your understanding:

  1. How do you identify when a differential equation is linear?
  2. What is an integrating factor, and why is it used in solving linear differential equations?
  3. Can you solve dydx=3xy\frac{dy}{dx} = 3x - y with initial condition y(0)=2y(0) = 2?
  4. How does the method of integration by parts work in more complex integrals?
  5. What is the significance of the initial condition in solving differential equations?

Tip: When solving differential equations, always verify that your solution satisfies both the differential equation and the initial condition.

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Math Problem Analysis

Mathematical Concepts

Differential Equations
First-Order Linear Differential Equations
Integration by Parts

Formulas

First-order linear equation: dy/dx + P(x)y = Q(x)
Integrating factor: μ(x) = e^∫P(x)dx
Integration by parts: ∫u dv = uv - ∫v du

Theorems

Linear first-order differential equations
Initial condition theorem

Suitable Grade Level

Undergraduate Mathematics