javescript //range_bar $x_0 =$ $y_0 =$ $\color{red}a_1 =$ $\color{red}b_1 =$ $\color{blue}a_2 =$ $\color{blue}b_2 =$ ${\color{red}(1)}-t\color{blue}(2)$ $t=$ $a(x-x_0)+b(y-y_0)=0$
