If the line l_1: 3 y-2 x=3 is the angular bisector of the lines l_2: x-y+1=0 and l_3: α x+β y+17=0, then α^2+β^2-α-β is equal to ____.

If the line $\displaystyle l_1: 3 y-2 x=3$ is the angular bisector of the lines $\displaystyle l_2: x-y+1=0$ and $\displaystyle l_3: \alpha x+\beta y+17=0$, then $\displaystyle \alpha^2+\beta^2-\alpha-\beta$ is equal to $\displaystyle \_\_\_\_$.