Solve the differential equation by separation of variables: . Which of the following is the general solution?
Table of contents
- 0. Functions7h 52m
- Introduction to Functions16m
- Piecewise Functions10m
- Properties of Functions9m
- Common Functions1h 8m
- Transformations5m
- Combining Functions27m
- Exponent rules32m
- Exponential Functions28m
- Logarithmic Functions24m
- Properties of Logarithms34m
- Exponential & Logarithmic Equations35m
- Introduction to Trigonometric Functions38m
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- Trigonometric Identities47m
- Inverse Trigonometric Functions48m
- 1. Limits and Continuity2h 2m
- 2. Intro to Derivatives1h 33m
- 3. Techniques of Differentiation3h 18m
- 4. Applications of Derivatives2h 38m
- 5. Graphical Applications of Derivatives6h 2m
- 6. Derivatives of Inverse, Exponential, & Logarithmic Functions2h 37m
- 7. Antiderivatives & Indefinite Integrals1h 26m
- 8. Definite Integrals4h 44m
- 9. Graphical Applications of Integrals2h 27m
- 10. Physics Applications of Integrals 3h 16m
- 11. Integrals of Inverse, Exponential, & Logarithmic Functions2h 34m
- 12. Techniques of Integration7h 39m
- 13. Intro to Differential Equations2h 55m
- 14. Sequences & Series5h 36m
- 15. Power Series2h 19m
- 16. Parametric Equations & Polar Coordinates7h 58m
13. Intro to Differential Equations
Basics of Differential Equations
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Solve the differential equation using the method of variation of parameters. Which of the following is the general solution?
A
B
C
D

1
Step 1: Start by solving the corresponding homogeneous equation. The given differential equation is 5y'' - 10y' + 10y = e^x sec(x). For the homogeneous part, set the right-hand side to 0: 5y'' - 10y' + 10y = 0. Solve this characteristic equation: 5r^2 - 10r + 10 = 0.
Step 2: Solve the characteristic equation 5r^2 - 10r + 10 = 0. Divide through by 5 to simplify: r^2 - 2r + 2 = 0. Use the quadratic formula r = (-b ± √(b^2 - 4ac)) / 2a, where a = 1, b = -2, and c = 2. Compute the discriminant b^2 - 4ac = (-2)^2 - 4(1)(2) = -4, which is negative. This indicates complex roots.
Step 3: The roots of the characteristic equation are r = 1 ± i. The general solution to the homogeneous equation is then y_h(x) = e^x(C_1 cos(x) + C_2 sin(x)), where C_1 and C_2 are constants determined by initial conditions.
Step 4: To solve the non-homogeneous equation using the method of variation of parameters, assume a particular solution of the form y_p(x) = u_1(x)e^x cos(x) + u_2(x)e^x sin(x), where u_1(x) and u_2(x) are functions to be determined. Substitute y_p(x) into the original equation and use the Wronskian of the solutions e^x cos(x) and e^x sin(x) to find u_1'(x) and u_2'(x).
Step 5: Compute u_1'(x) and u_2'(x) using the formulas u_1'(x) = -y_2(x)g(x)/W(x) and u_2'(x) = y_1(x)g(x)/W(x), where y_1(x) = e^x cos(x), y_2(x) = e^x sin(x), g(x) = e^x sec(x), and W(x) is the Wronskian of y_1 and y_2. Integrate u_1'(x) and u_2'(x) to find u_1(x) and u_2(x), then substitute back into y_p(x). Combine y_h(x) and y_p(x) to form the general solution.
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