Answer
$(a+bi)+(a-bi)=a+a+bi-bi=a+a=2a$
Work Step by Step
If the complex number z is represented by $a+bi$ then its conjugate is $a-bi$.
Add the complex number and its conjugate:
$(a+bi)+(a-bi)$
=$a+a+bi-bi$
=$a+a$
=$2a$.
Since $a$ is a real number, the sum of z and its conjugate is also a real number.
