题是这个意思吗?(1+2i)/(a+bi) =1+i
a+bi=(1+2i)/(1+i)
=[(1+2i)(1-i)]/[(1+i)(1-i)]
=[1+i-2i^2]/[1-i^2]
=(3+i)/2
=3/2+i/2
a=3/2,b=1/2