NDA2019MathematicsQuadratic EquationActual
If and are the roots of x^2+x+1=0 , then what is _ j=0 ^3 ( ^j+ ^j ) equal to?
Options
- A8
- B6
- C4
- D2
Correct answer
D. 2
Step-by-step solution
x^2+x+1=0 = and = ^2 _ j=0 ^3 ( ^j+ ^j )= ( ^0+ ^1+ ^2+ ^3 )+ ( ^0+ ^1+ ^2+ ^3 ) sum of 3 consecutive powers of and =0 _ j=0 ^3 ( ^j+ ^j )= ^0+ ^0=2