Re: Help resolving the following equation...

[Francesco Potortì]

>I am trying to determine an interest rate by solving the following equation:
>*fsolve(@(r) 200*(1+r)^(4)+300*(1+r)^(3)+400*(1+r)^(2)+500*(1+r)^(1)-1000,0)
>*
>What really puzzles me is that Octave will not give me a solution that makes
>sense: it gives me a negative interest rate!!
>In plain English, the problem is as follows: one invests 1000$ at year 1,
>and receives 200 at year 2, 300 at year 3, 400 at year 4 and 500 at year 5.
>I have to find out the interest rate of this investment...

What you are solving is this problem:

year    money
-4      200
-3      300
-2      400
-1      500
now     -1000

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