showing roots of an equation

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metin yilmaz
metin yilmaz on 10 Nov 2020
Commented: Walter Roberson on 10 Nov 2020
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?

Accepted Answer

KSSV
KSSV on 10 Nov 2020
Edited: KSSV on 10 Nov 2020
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)
  4 Comments
metin yilmaz
metin yilmaz on 10 Nov 2020
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 on 10 Nov 2020
solve(d)
That does not change d. You would have needed
d = solve(d)

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