complex numbers

[yang_dong]

if a and b are complex numbers, Im(a) = 2, Re(b) = -1 and a+b=-ab, find and b

Thanks in advance

[RKTR]

a= x+2 i 
b= -1 +yi

(x-1) +(2+y)i =-(x+2i)(-1+yi)
(x-1)+(2+y)i =-(-x-2i+xyi-2y)
(x-1)+(2+y)i=(x+2y)+(2-xy)i

x-1=x+2y  y=-1/2

2+y=2-xy
y=-xy
-x=1 x=-1

a: -1 + 2i , b: -1 -1/2 i