Answer
(a) $-3-2i$
(b) $2+8i$
Work Step by Step
(a) $(3-6i)-(6-4i)=3-6-6i+4i=-3-2i$
(b) $4i(2- \frac{1}{2}i)=8i-2i^{2}=8i-2*-1=8i+2=2+8i$
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