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showing roots of an equation

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metin yilmaz
metin yilmaz 2020-11-10
评论： Walter Roberson 2020-11-10
Would you please explain what is wrong with this operation? I entered an equation as a string and then assigned it
to a variable named d. Then I used that variable in the solve command and since there are two roots I considered d as a
struct with two fields. Is this correct? Is d a struct or not? Then I tried to show roots as fields by writing d(1) and d(2)
but the operations gave very strange results in the following.
>> d='x^2-6*x-12'
d =
'x^2-6*x-12'
>> solve(d)
ans =
3 - 21^(1/2)
21^(1/2) + 3
>> d(1)
ans =
'x'
>> d(2)
ans =
'^'
Would you also please introduce some other methods to show roots?

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采纳的回答

KSSV
KSSV 2020-11-10
编辑：KSSV 2020-11-10
Write the coefficients of your polynomial as an array ans use roots.
p = [1 -6 -12] ;
s = roots(p)
Use symbolic
syms x
p = x^2-6*x-12 ==0 ;
s = solve(p)
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metin yilmaz
metin yilmaz 2020-11-10
Okay, thank, so without introducing x as symbolic by syms, d(1) and d(2) only give the elements of the string assigned to the varible? Right?
Walter Roberson
Walter Roberson 2020-11-10
solve(d)
That does not change d. You would have needed
d = solve(d)

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