If x^3 = 1 and x does not equal 1, x(x+1)= ?
Do it in polar:
x^3=1@0=1@360= 1@720
x= 1@0 not allowed in the problem statement
other solutions...
x= 1@120= 1cos120+i*sin120=you do it.
x=1@240=1cos240+i*sin240= you do it.
now, with the last two, solve for x(x+1)
have fun.