Without expanding the determinants show that
1 w w2
w w2 1
w2 1 w
=0 where w is one of the cube roots of unity.
(w2 means w square )
apply R1--->R1+R2+R2 you will get first column as 1+w+w2 which is equal to zero.
NOTE:if w is the cube root of unity the 1+w+w2 =0.