Most Important Selected Qs for JEE AdvancedMathematicsComplex Number
Paragraph Roots of z^n-1=0 are 1, , ^2, ^3, . . ^ n-1 where = 2 n +i 2 n so z^n-1=(z-1)(z- ) ( z - ^ n -1 ) On the basis of above information, answer the following questions : Question If n =7 , then the equation whose roots are + ^2+ ^4 and ^3+ ^5+ ^6 is -
Options
- Ax^2-x+2=0
- Bx^2+x-2=0
- Cx^2-x-2=0
- Dx^2+x+2=0
Correct answer
D. x^2+x+2=0
Step-by-step solution
n =7, ^7=1 and 1+ + ^2+ . . ^6=0 Sum of the roots = + ^2+ ^4+ ^3+ ^5+ ^6=-1 Product of the roots = ( + ^2+ ^4 ) ( ^3+ ^5+ ^6 )= ^4+ ^6+ ^7+ ^5+ ^7+ ^8+ ^7+ ^9+ ¹⁰=2+ (1+ + ^2+ ^3+ ^4+ ^5+ ^6 )=2 So the required equation is x^2-(-1) x+2=0 x^2+x+2=0