Answer
See below.
Work Step by Step
$x+\overline{x}=(a+bi)+\overline{a+bi}=(a+bi)+(a-bi)=a+a+bi-bi=2a$
$x-\overline{x}=(a+bi)-\overline{a+bi}=(a+bi)-(a-bi)=a-a+bi+bi=2bi$
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