How Does a Differential Equation Model Disease Spread?

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The spread of a disease in a community is modeled by the following differential equation:

dy/dx = 0.2y - 0.02x where y is the number of infected individuals in thousands, and x the time in days.

2) Solve the equation, using the linear 1st order method, given that initially there are 1000 infected individuals?

How do I do that? :cry:
 
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How about doing what you were told to do? Since the problem says "using the linear 1st order method", I presume that you are expected to learn that there is a simple way (in fact, a formula) for finding an integrating factor for the differential equation. Check your textbook for that formula.
 
http://www.ucl.ac.uk/Mathematics/geomath/level2/deqn/de8.html
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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