How to distinguish exact roots using Solve?

[aheight]

Can someone help me distinguish when Solve[polynomial==0,x] returns exact solutions as opposed to solutions in terms of Roots? For example, if I code:

myroots = x /. Solve[1/2 + 1/5 x + 9/10 x^2 + 2/3 x^3 - 1/5 x^4 + 3/11 x^5 == 0, x]

this cannot be solved in terms of radicals so Solve returns Root objects:

{Root[165+66 #1+297 #1^2+220 #1^3-66 #1^4+90 #1^5&,1],
Root[165+66 #1+297 #1^2+220 #1^3-66 #1^4+90 #1^5&,2],
Root[165+66 #1+297 #1^2+220 #1^3-66 #1^4+90 #1^5&,3],
Root[165+66 #1+297 #1^2+220 #1^3-66 #1^4+90 #1^5&,4],
Root[165+66 #1+297 #1^2+220 #1^3-66 #1^4+90 #1^5&,5]}

but
myroots = x /. Solve[1/2 + 1/5 x + 9/10 x^2 + 2/3 x^3 - 1/5 x^4 == 0, x]

returns exact solutions in terms of radicals. I can't figure out how to distinguish the two as in:

If[solve returns exact solutions,
do this;
,
else if Roots are returned do this
]

Can someone help me do this?

 

[Dale]

A Root is an exact numeric quantity. You can use N on it to get an approximate value to any degree of precision needed. You can also use ToRadicals on it if needed.

 

[Ben Niehoff]

You should read the help files on pattern matching. The pattern which matches a Root object is "_Root". Or you can use Head, which returns the head of an expression:

If[Head[expr]===Root, ...]