Observe the graph:
The graph represent the parabola.
The graph represents a function because each -value is paired with one -value.
![\"\"](\"/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=8da2268e35b6b6daab9c47f71c4c8bf4.png\")
-value is paired with one ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=b1f02a70f7489dd3b8742e9e1c94d6d0.png\")
-value.![\"\"](\"/userfiles/image/steps_images/solution.JPG\")
-value is paired with one -value.