[tex]\begin{gathered} \text{ The equation of a line is} \\ y=mx+b \\ \\ m=\frac{y_2-y_1_{}_{}}{x_2-x_1} \\ m=\frac{3-0}{3-0} \\ \\ m=\frac{3}{3} \\ m=1 \\ \\ \text{Then y=x+b} \\ \\ \text{but } \\ 0=0+b \\ 0=b \\ \text{Thus the equation is} \\ \\ y=x \end{gathered}[/tex]
