The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have:
[tex]\left(\dfrac{2}{3},\ \dfrac{4}{7}\right)\to x_1=\dfrac{2}{3},\ y_1=\dfrac{4}{7}\\\\\left(\dfrac{2}{3},\ \dfrac{11}{7}\right)\to x_2=\dfrac{2}{3},\ y_2=\dfrac{11}{7}[/tex]
Substitute
[tex]m=\dfrac{\dfrac{11}{7}-\dfrac{4}{7}}{\dfrac{2}{3}-\dfrac{2}{3}}=\dfrac{\dfrac{7}{7}}{0}\qquad\boxed{!!!!}[/tex]
Answer: The slope is not defined.
