Exercise 9 Page 379

By graphing the given equations, we can determine the number of solutions to the system. This will be the point at which the lines intersect. To do this, we will need the equations to be in slope-intercept form to help us identify the slope $m$ and $y -$ intercept $b .$

Write in Slope-Intercept Form

Let's rewrite each of the equations in the system in slope-intercept form, highlighting the $m$ and $b$ values.

Given Equation	Slope-Intercept Form	Slope $m$	$y -$ intercept $b$
$x - y = 1$	$y = 1 x + (- 1)$	$1$	$(0, - 1)$
$x + y = 5$	$y = - 1 x + 5$	$- 1$	$(0, 5)$

Graphing the System

To graph these equations, we will start by plotting their $y -$ intercepts. Then, we will use the slope to determine another point that satisfies each equation, and connect the points with a line.

We can see that the lines intersect at exactly one point.

The point of intersection at $(3, 2)$ is the one solution to the system.