TI-Nspire enables you to view the residual squares on a moveable line. Press [MENU]→Analyze→Residuals→Show Residual Squares to view the residual squares of a movable line. Each square has sides whose length equals the difference between the y-value of a given data point and the corresponding y-value on the movable line.
The sum of the areas of the residual squares is also displayed on the screen. The least squares regression line is the line for which the sum of the residual squares is minimized. Grab the movable line to get as small a sum as possible.
Try pressing [MENU]→Analyze→Residuals→Show Residual Plot. As shown in the last screen, this action produces a scatter plot of the residuals. Don’t forget to try dragging the movable line to observe the corresponding changes to the residual plot.
Move your cursor to the movable line and press [CTRL][MENU] to bring up the context menu. The context menu gives you the choice of removing the movable line and hiding or showing the residual squares and the residual plot.