AP EAMCET2010MathematicsComplex Number
If is a complex cube root of unity, then (x+1)(x+ )(x- -1) is equal to
Options
- Ax^3-1
- Bx^3+1
- Cx^3+2
- Dx^3-2
Correct answer
A. x^3-1
Step-by-step solution
cube root of unity ie, ^3=1 and 1+ + ^2=0 Then, (x+1)(x+ )(x- -1)=(x+1) (x^2+ x- x- ^2-x- )=(x+1) (x^2-x- ( + ^2 ) )=(x+1) (x^2-x-(-1) ) ( + ^2=-1 )=(x+1) (x^2-x+1 )=(x+1) (x^2+1-x )= (x^3-1 )