# A Course in Ordinary Differential Equations by Swift, Randall J.; Wirkus, Stephen A By Swift, Randall J.; Wirkus, Stephen A

Compliment for the 1st Edition:""A direction in traditional Differential Equations merits to be at the MAA's simple Library checklist ... the e-book with its format, is particularly scholar friendly-it is simple to learn and comprehend; each bankruptcy and reasons circulate easily and coherently ... the reviewer could suggest this publication hugely for undergraduate introductory differential equation courses."" -Srabasti Dutta, collage of Saint Read more...

summary: compliment for the 1st Edition:""A path in usual Differential Equations merits to be at the MAA's easy Library checklist ... the booklet with its format, is especially pupil friendly-it is straightforward to learn and comprehend; each bankruptcy and motives stream easily and coherently ... the reviewer could suggest this booklet hugely for undergraduate introductory differential equation courses."" -Srabasti Dutta, university of Saint Elizabeth, MAA on-line, July 2008""An vital characteristic is that the exposition is richly followed by means of laptop algebra code (equally disbursed among MATLAB, Mathematica, and Maple

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Extra resources for A Course in Ordinary Differential Equations

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What we really need is a method for testing a differential equation for exactness and for constructing the corresponding function F (x, y). Both are contained in the following theorem and its proof. 5. 27) where M and N have continuous first partial derivatives at all points (x, y) in a rectangular domain D. 28) for all (x, y) in D. Remark: The proof of this theorem is rather important, as it not only provides a test for exactness, but also a method of solution for exact differential equations.

The decay law states that the amount of radioactive substance that decays is proportional at each instant to the amount of substance present. 18. The strength of a radioactive substance decreases 50% in a 30-day period. How long will it take for the radioactivity to decrease to 1% of its initial value? 19. 44 mg in 1 year. What length of time elapses before the radioactivity decreases to half its original value? 20. A tin organ pipe decays with age as a result of a chemical reaction that is catalyzed by the decayed tin.

Dx Solution We can easily verify that y1 = e2x and y2 = 5x − 5 are the solutions of the respective differential equations. Let Q1 (x) = 3e2x , Q2 (x) = 5x, and Q(x) = e2x +4x denote the right-hand sides of the three differential equations. We observe that 1 4 Q(x) = Q1 (x) + Q2 (x). 3 5 By superposition, it follows that y= 1 4 1 4 y1 + y2 = (e2x ) + (5x − 5) 3 5 3 5 is a solution of y + y = Q(x). Integrating Factor Technique In studying separable equations, we put all the terms of one variable on the left side of the equation and the terms of the other variable on the right side of the equation.