First, we simplify i12. We know that i2=−1, i3=−i, i4=1. Since 12 is a multiple of 4, i12=(i4)3=13=1. Therefore, 0.5i12=0.5(1)=0.5. Next, we expand the numerator of the fraction:
(3i+1)(i−3)=3i2−9i+i−3=3(−1)−8i−3=−3−8i−3=−6−8i. So the expression becomes 0.5+i−1−6−8i. To simplify the fraction, we multiply the numerator and denominator by the conjugate of the denominator, which is −i−1 or −1−i. i−1−6−8i=i−1−6−8i⋅−1−i−1−i=(i−1)(−1−i)(−6−8i)(−1−i)=−i−i2+1+i6+6i+8i+8i2=−i−(−1)+1+i6+14i+8(−1)=−i+1+1+i6+14i−8=2−2+14i=−1+7i. Finally, we add the two parts together:
0.5+(−1+7i)=0.5−1+7i=−0.5+7i.