Let and be the sum and the product of all the non-zero solutions of the equation ( z)2+|z|=0, z . Then 4( 2+ 2) is equal to :
- 4
- 2
- 6
- 8
Answer
(1) 4
Solution
Let z=x+iy ( z)2=x2-y2-2ixy
(x2-y2+ x2+y2 )-2ixy=0 xy=0
y=0: x2+|x|=0 x=0 (rejected, z 0)
x=0: -y2+|y|=0 |y|=1 z= i
=i+(-i)=0, =i(-i)=1
4( 2+ 2)=4(0+1)=4
Answer: (1)