Complex Numbers Q

We have $O(0), \ P(\alpha), \ Q(\beta), \ M\left(\frac{\alpha+\beta}{2}\right), \ N\left(\frac{\alpha}{2}\right), \ R(z)$ .

Let $\frac{NR}{RQ}=k, \ \frac{MR}{RO}=k_1$ . Then

$z=\frac{z_N+kz_Q}{1+k}=\frac{\alpha}{2(1+k)}+\frac {\beta k}{1+k}$

and $z=\frac{z_M+k_1z_O}{1+k_1}=\frac{\alpha}{2(1+k_1)} +\frac{\beta}{2(1+k_1)}$

Then $\left\{\begin{array}{ll}\frac{1}{2(1+k)}=\frac{1}{ 2(1+k_1)}\\\frac{k}{1+k}=\frac{1}{2(1+k_1)}\end{ar ray}\right.$

$\Rightarrow k=k_1=\frac{1}{2}\Rightarrow z=\frac{1}{3}(\alpha+\beta)$ .