showing roots of an equation

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?

Answer 1

[KSSV]

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)

[metin yilmaz]

Thank very much for introducing those methods and yours work when writing d(1) and d(2). Do you have any idea that why my methods didn't work with d(1) and d(2) even though I was able to solve the equation to find roots.

[KSSV]

You have to use syms.

[metin yilmaz]

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]

solve(d)

That does not change d. You would have needed

d = solve(d)