Z=m^2(1+i)/(m+5)+(8m+15)i+(m-6)/(m+5)=(m^2+m-6)/(m+5)+[8m+15+(m^2)/(m+5)]i要使Z为虚数,即8m+15+(m^2)/(m+5)=0(8m+5)(m+5)+m^2=09m^2+45m+25=0解得m=(-45±15√5)/18