由题设知,x∈R,x≠0.且x^2-zx+4+3i=0.===>z=[x+(4/x)]+(3/x)i.===>18=|z|^2=[x+(4/x)]^2+(3/x)^2.===>x^2=5.===>z=(9+3i)/x===>z=±(√5)(9+3i)/5.