Given, equation is x11−x7+x4−1=0 ⇒x7(x4−1)+1(x4−1)=0 ⇒(x7+1)(x4−1)=0 If x7+1=0, then x7=−1 x7=−1=cosπ+isinπ x7=cos(2k+1)π+isin[2k+1)π x=[cos(2k+1)π+isin(2k+1)π]
1
7
x=cos(2k+1)
π
7
+isin(2k+1)
π
7
where, k=0,1,2,3,4,5,6 If x4−1=0 x4=1=cos0+isin0 x4=cos2kπ+isin2kπ x=(cos2kπ+isin2kπ)