Is it possible to get multiple 0s from fzero?

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Cassandra Meyer 2022-1-30

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https://ww2.mathworks.cn/matlabcentral/answers/1639345-is-it-possible-to-get-multiple-0s-from-fzero

评论： Cassandra Meyer 2022-1-31

I have already found the three zeros of this function by setting it to 0, and I am told to use fzero to and compare the two values. However, I have seen a question or two mentioning that I cannot get multiple zeros from fzero. Do I run this three times in separate intervals or is there another way?

fun = @(x) x^3 -4*x^2 +1;
x0 = [-5 5]; % initial interval
x = fzero(fun,x0)

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Answer 1

Sulaymon Eshkabilov 2022-1-31

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https://ww2.mathworks.cn/matlabcentral/answers/1639345-is-it-possible-to-get-multiple-0s-from-fzero#answer_885035

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In your exercise, ie. a polynomial, the first try is roots() and then fzero() with different intervals can be an option for real roots.

SOls = roots([1 -4 0 1])
SOls = 3×1
    3.9354
    0.5374
   -0.4728
fun = @(x) x^3 -4*x^2 +1;
X01 = [2 5];
x1 = fzero(fun,X01)
x1 = 3.9354
X02 = [0 2];
x2 = fzero(fun,X02)
x2 = 0.5374
X03 = [-1 0];
x3 = fzero(fun,X03)
x3 = -0.4728