# how to solve the following equation?

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kimy on 24 Nov 2021
Commented: Star Strider on 25 Nov 2021
Dear all,
I have a easy question since I am not familiar with matlab. Hope you can give me some tips? My question is as belows.
a=[1,2,3];
a=((b-2).*(b+1))./((b+3).*(b-1)):
b=?
I would like to solve b. Should I use for loop and assume a initial value of b then solve it iteratively? but I forget how to achieve this programme. Thanks for your attention.

Star Strider on 24 Nov 2021
Try this —
a=[1,2,3];
afcn = @(b) ((b-2).*(b+1))./((b+3).*(b-1));
[estb,fval] = fminsearch(@(b) norm(afcn(b) - a), rand) % Estimate For All 'a'
estb = 0.7016
fval = 1.4142
for k = 1:numel(a)
[estba(k),fvala(k)] = fminsearch(@(b) norm(afcn(b) - a(k)), rand); % Estimate For All 'a'
end
estba
estba = 1×3
0.3333 0.7016 0.8117
fvala
fvala = 1×3
1.0e+-4 * 0.2770 0.1710 0.5080
bv = linspace(0, 1.5);
figure
plot(bv, afcn(bv))
hold on
plot(estb, afcn(estb), 'sr', 'MarkerSize',20)
plot(estba, afcn(estba), 'pg', 'MarkerSize',15, 'MarkerFaceColor','g')
hold off
grid
Experiment to get different results
.
##### 2 CommentsShowHide 1 older comment
Star Strider on 25 Nov 2021
As always, my pleasure!
.