Linear Differential Equation: Solving for M with Integrating Factor of .5

HerpaDerp
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Homework Statement



dM/dT = .5m-24

I know this is a linear differential equation, with an integrating factor of .5
I get my final answer to be M = 48+ke^(-.5t)

Next, when t = 0, M = 7e^(.5t)...

Giving me k = 7e^(.5t) - 48

so to solve for M..

M = 48 + (7e^(.5t)-48)e^(-.5t)

And finally I get 55-48e^(-.5t)=M which I guess isn't right. Anyone help out what I did wrong here?



My final answer that I get is 55-48e^(-.5t), which I guess is wrong. Where did I go wrong?
 
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The equation is separable. You don't really need an integrating factor. M=48+ke^(-.5t) is close, but you do you get the (-.5) factor in front of the t? That's wrong. And M=7*e^(.5t) at t=0 is kind of an odd way to state an initial condition. Do you mean M=7 at t=0?
 
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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