0 个投票

Hello, I'm trying to solve this equation using Matlab: (to find i)
But I can't understand the result that I get which is:
I'm only showing a part of the result. Any help to solve this equation is much appreciated.
syms i;
prt1=61466000*((1+i)^46-1)/(i*(1+i)^46);
prt2=400000000*(1+i)^-1;
prt3=500000000*(1+i)^-2;
prt4=760000000*(1+i)^-3;
prt5=200000000*(1+i)^-4;
prt6=140000000*(1+i)^-5;
prt7=3105237.5*((1+i)^46-1)/(i*(1+i)^46);
second=prt2+prt3+prt4+prt5+prt6+prt7;
eqn=prt1-second;
solve(eqn,i)

4 个评论
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Why do you delete the term (1+i)^-4 in your code ?
Dimitris Kalogiros
Dimitris Kalogiros 2018-9-20
Does i have to be positive integer ?
Nadun Chandrabahu
Nadun Chandrabahu 2018-9-20
Yeah I forgot to include this! Thanks for pointing it out. Torsten below gave me a solution which is correct I think, but could you help me to get the answer in 7 significant figures?
Nadun Chandrabahu
Nadun Chandrabahu 2018-9-20
@Dimitris Kalogiros, yeah it has to be a very small number between 0 and 0.1. I need it in 7 s.f

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 采纳的回答

Torsten
Torsten 2018-9-20

0 个投票

fun=@(i)400000000*(1+i)^-1+500000000*(1+i)^-2+760000000*(1+i)^-3+200000000*(1+i)^-4+140000000*(1+i)^-5+3105237.5*((1+i)^46-1)/(i*(1+i)^46)-61466000*((1+i)^46-1)/(i*(1+i)^46);
sol=fzero(fun,0.01)

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Nadun Chandrabahu
Nadun Chandrabahu 2018-9-20
Hey thanks for your answer!
I'd like to get this answer in 7 s.f, and as Cesar pointed out. I made an error when I wrote the equation. Forgot to include the terms: (1+i)^-4
I modified your equation to include this term. Could you please check it? Also I need this answer in 7 significant figures at least.
Thank you!
fun=@(i)400000000*(1+i)^-1+500000000*(1+i)^-2+760000000*(1+i)^-3+200000000*(1+i)^-4+140000000*(1+i)^-5+3105237.5*((1+i)^46-1)/(i*(1+i)^46)*((1+i)^-4)-61466000*((1+i)^46-1)/(i*(1+i)^46)*((1+i)^-4);
sol=fzero(fun,0.01)
Nadun Chandrabahu
Nadun Chandrabahu 2018-9-20
Right now when I solve it, I get 0.0124 which is correct. Just need more accuracy :)
Torsten
Torsten 2018-9-20
format long
fun=@(i)400000000*(1+i)^-1+500000000*(1+i)^-2+760000000*(1+i)^-3+200000000*(1+i)^-4+140000000*(1+i)^-5+3105237.5*((1+i)^46-1)/(i*(1+i)^46)*(1+i)^-4-61466000*((1+i)^46-1)/(i*(1+i)^46)*(1+i)^-4;
sol=fzero(fun,0.01)

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