JEE Main2004MathematicsComplex NumberActual
If z=x-i y and z^ 1 3 =p+i q , then ( x p + y q ) (p^2+q^2 ) is equal to
Options
- A1
- B-2
- C2
- D-1
Correct answer
B. -2
Step-by-step solution
z=(p+i q)^3=p (p^2-3 q^2 )-i q (q^2-3 p^2 ) x p =p^2-3 q^2 & y q =q^2-3 p^2 x p + y q (p^2+q^2 ) =-2