Let A (1,0), B (2,-1) and C (7/3, 4/3) be three points. If the equation of the bisector of the angle ABC is α x+β y=5, then the value of α^2+β^2 is

Let $\displaystyle \mathrm{A}(1,0), \mathrm{B}(2,-1)$ and $\displaystyle \mathrm{C}\left(\frac{7}{3}, \frac{4}{3}\right)$ be three points. If the equation of the bisector of the angle ABC is $\displaystyle \alpha x+\beta y=5$, then the value of $\displaystyle \alpha^2+\beta^2$ is