If you want to evaluate a function
at a specific point
, you'll have to look for
on the x axis, and then look vertically for the point on the graph.
The y coordinate of that point is the corresponding y value.
So, for example, if we want
, we start from the origin and go up, until we find the point
that belongs to the graph. So, we have
.
Similarly, for
, we start from 2 on the x axis and go up until we meet the point
on the graph. So, we have
.
For
, we start from -8 on the x axis and go up until we meet the point
on the graph. So, we have
.
For
, we start from -6 on the x axis and go down until we meet the point
on the graph. So, we have
.
The three x-values for which the corresponding y-value is zero are the x-coordinates of the points where the graph crosses the x axis (this means that the y axis is zero). Those three points are
![(-7, 0),\ (-2, 0),\ (4, 0)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/oeuz3sro50yidtwmy355u6iih38ppmgv1w.png)