c++ 两个复数 c1-=c2 、c1/=c2 算出来都等于c1，这是怎么算的

c1 -= c2 , c1= c1 -c2, assume ans c1 = c3, then c3 = c1 - c2
c1/=c2,c3 = c1/c2, then c1/c2 = c1 -c2, c1 = c2(c1-c2), c1(c2-1) = c2*c2, c1 = (c2*c2)/(c2-1), then if c2 = 10, c1 = 100/9