Solving Initial Value Problem for Exponential Growth

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Homework Statement
To encourage buyers to place 100-unit orders, your firm's sales department applies a continuous discount that makes the unit price a function p(x) of the number of units x ordered. The discount decreases the price at a rate of $0.01 per unit ordered. The price per unit for a 100-unit order is p(100) = $20.09. Find p(x) by solving the following initial value problem:

Differential equation: dp/dx = -p/100
Initial condition: p(100) = 20.09


The attempt at a solution
So I integrated the differential equation and applied the initial condition to it. I was able to get the following equation:

p = 20.09e^{1 - x/100}

Is this correct?
 
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Yes, it's correct. You can verify it by confirming that it satisfies the differential equation and the initial condition.
 
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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