In: Advanced Math
Question 1:
a) What are the complex roots of x^8-1 ?
b) What are the irreducible factors of f(x)=x^8-1 in R[x]?
c) What are the irreducible factors of f(x)=x^8-1 in Q[x]?
(a) We have to find out complex root of 
now 

  
......................................(1)
Thus we have  
also, 
Again we have 

where n be integer
  so we have n=0,1,2,3
when n=0 then

When n=1

when n=2

when n=3

Hence we got the complex root are
and 
(b) Form (1) we seen that 
 so the irreducable factor of 
 in 
 is 
 and 
(c) Here also irreduciable factor of 
 in 
 is 
 and