Q.If $z_1=3+2i$ and $z_2=1-i$, verify that $\overline{z_1z_2}=\bar z_1\,\bar z_2$.

A complex number is an expression $z=a+ib$, where $a,b$ are real numbers and $i$ is the imaginary unit defined by $i^2=-1$. The number $a=\mathrm{Re}(z)$ is its real part and $b=\mathrm{Im}(z)$ is its imaginary part; two complex numbers are equal exactly when both parts match separately. Complex numbers were introduced precisely because equations like $x^2+1=0$ have no real solution — the real numbers cannot supply a square root of a negative number, but $\mathbb{C}$ can. Addition and subtraction combine real parts with real parts and imaginary parts with imaginary parts: $(a+ib)\pm(c+id)=(a\pm c)+i(b\pm d)$. Multiplication expands like ordinary binomials with the substitution $i …