First slide
De-moivre's theorem
Question

If x=ωω22 then the value of x4+3x3+2x211x6 is (where ω is cube root of unity)______

Moderate
Solution

We have 
x=ωω22 or x+2=ωω2
Squaring,x2+4x+4=ω2+ω42ω3=ω2+ω2=3
x2+4x+7=0
Dividing x4+3x3+2x211x6 by x2+4x+7 we get
x4+3x3+2x211x6=x2+4x+7x2x1+1=(0)x2x1+1=0+1=1

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