How to solve an equation with one variable (x) including a "sum" from 1:n?

Question

Tim 2014-4-18

评论： Mário Vieir 2018-7-7

Hi, I never used Matlab to solve simple equations, so it would be awesome if anyone could help me out:

I want to get to know "x", the "sum" is going from 1:n (so for example from 1:4..1,2,3,4). I've given data like:

    K=[100 120 160 100]
    Z=[100 100 170 700]
    n=1:4

Variable: x

I want to solve this equation:

sum( (Z(n)/1.03^n) + ( ( x/4 - (x*(5-n)/4)*1.02) / 1.05^n ) == 0 )

Is that possible with Matlab? I tried the smys x and solve() function but that didn't work...

Thanks a lot!

Answer 1

Mischa Kim 2014-4-18

编辑：Mischa Kim 2014-4-18

Tim, is the sum of all the 4 equation terms supposed to be equal to zero? If so, this should do

 syms x
 sol = vpa(sum((Z./1.03.^n) + ((x/4 - (x.*(5-n)/4)*1.02)./1.05.^n )) == 0)

Tim 2014-4-18

Mischa, Thank you so much, that works perfectly fine! Thanks a lot!

Mário Vieir 2018-7-7

Thank you.