Chapter 1.1, Problem 39E

Using the Midpoint Formula Show that $\left(\frac{1}{3}\left[2x_1+x_2\right],\frac{1}{3}\left[2y_1+y_2\right]\right)$ is one of the points of trisection of the line segment joining $\left(x_1,y_1\right)$ and $\left(x_2,y_2\right)$

Then, find the second point of trisection by finding the midpoint of the line segment joining

$\left(\frac{1}{3}\left[2x_1+x_2\right],\frac{1}{3}\left[2y_1+y_2\right]\right)$ and $\left(x_2,y_2\right)$