Math Problem Statement

Solve the following IVP and give the constants k1 and k2 of the particular solution: d²y/dt² + 7dy/dt + 10y = 0, with y(0) = 3 and y'(0) = 2.

Solution

To solve this initial value problem (IVP), we need to solve the second-order differential equation and then use the initial conditions to determine the constants k1k_1 and k2k_2.

The differential equation is: d2ydt2+7dydt+10y=0\frac{d^2 y}{dt^2} + 7 \frac{dy}{dt} + 10y = 0 with the initial conditions: y(0)=3andy(0)=2y(0) = 3 \quad \text{and} \quad y'(0) = 2

Step 1: Solve the Characteristic Equation

The characteristic equation for the differential equation is: r2+7r+10=0r^2 + 7r + 10 = 0

Solving this quadratic equation: r=7±49402=7±32r = \frac{-7 \pm \sqrt{49 - 40}}{2} = \frac{-7 \pm 3}{2} This gives the roots: r1=2andr2=5r_1 = -2 \quad \text{and} \quad r_2 = -5

Step 2: General Solution of the Differential Equation

Since we have two distinct real roots, the general solution is: y(t)=k1e2t+k2e5ty(t) = k_1 e^{-2t} + k_2 e^{-5t}

Step 3: Apply Initial Conditions

  1. Using y(0)=3y(0) = 3: y(0)=k1e0+k2e0=k1+k2=3y(0) = k_1 e^0 + k_2 e^0 = k_1 + k_2 = 3

  2. Using y(0)=2y'(0) = 2: First, find y(t)y'(t): y(t)=2k1e2t5k2e5ty'(t) = -2k_1 e^{-2t} - 5k_2 e^{-5t} Then apply t=0t = 0: y(0)=2k15k2=2y'(0) = -2k_1 - 5k_2 = 2

Step 4: Solve the System of Equations

We now have the system:

  1. k1+k2=3k_1 + k_2 = 3
  2. 2k15k2=2-2k_1 - 5k_2 = 2

Solving for k1k_1 and k2k_2:

  • From equation (1): k1=3k2k_1 = 3 - k_2

  • Substitute k1k_1 in equation (2): 2(3k2)5k2=2-2(3 - k_2) - 5k_2 = 2 6+2k25k2=2-6 + 2k_2 - 5k_2 = 2 3k2=8-3k_2 = 8 k2=83k_2 = -\frac{8}{3}

  • Substitute k2=83k_2 = -\frac{8}{3} back into equation (1): k1+(83)=3k_1 + \left(-\frac{8}{3}\right) = 3 k1=3+83=173k_1 = 3 + \frac{8}{3} = \frac{17}{3}

Solution

The constants are: k1=173andk2=83k_1 = \frac{17}{3} \quad \text{and} \quad k_2 = -\frac{8}{3}

Would you like a detailed explanation of any step?


Here are 5 related questions to deepen understanding:

  1. How does the method change if the characteristic equation has complex roots?
  2. What would happen if the initial conditions were different, e.g., y(0)=0y(0) = 0 and y(0)=1y'(0) = 1?
  3. Can we verify the solution by plugging it back into the original differential equation?
  4. How would the solution form change if the equation had repeated roots?
  5. Why are initial conditions necessary to find a particular solution?

Tip: Always check if the characteristic equation has real, complex, or repeated roots, as this affects the general solution structure.

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Math Problem Analysis

Mathematical Concepts

Differential Equations
Initial Value Problems
Characteristic Equations

Formulas

d²y/dt² + 7dy/dt + 10y = 0
Characteristic equation: r^2 + 7r + 10 = 0

Theorems

Solving homogeneous linear differential equations

Suitable Grade Level

College level - Calculus