$\"\"$

Graph each inequality. The intersection of graphs forms a tetrahedral. $\"system$ $\"\"$

The coordinates (1, 9) ( $\"\"$ 4, 3) and (1, $\"\"$ 2) can be determinated from the graph.

To find the fourth vertex, solve the system of equations $\"\"$ and $\"\"$ .

Adding the two equations $\"\"$ and $\"\"$ .

$\"\"$

Substitute $\"\"$ in $\"\"$ then

$\"\"$

The fourth vertex is $\"\"$ . $\"\"$

Check:

Compare the coordinates to the coordinates on the graph.

The x- coordinate of the third vertex is at 7.

The y- coordinate of the third vertex is at 4. $\"\"$

The vertices of a triangle are at $\"\"$ .