9.计算:(1)+6;
(2)+2+.
[解] (1)原式=+i66
=i+i2=i-1.
(2)原式=++
=i++
=i+(-i)+0=0.
10.(1)若=-i,求实数a的值;
(2)若复数z=,求+3i.
[解] (1)依题意,得2+ai=-i(1+i)=2-i,
∴a=-.
(2)∵z==
=i(1+i)=-1+i,
∴=-1-i,
∴+3i=-1+2i.
[能力提升练]
1.计算+的值是( )
A.0 B.1