Now let's look at the differences. First we will study what happens as we move left on the graphs.
When we move to the left on a line slanting up we also move downwards. Moving to the left on a line that slants down will also make us move upwards. Next we will look at the graphs as we move right.
When we move to the right on a line slanting up, we at the same time move up. When we move to the right on a line slanting down we also move down. Another way to express this is that a line that slants up increases and that a line that slants down decreases across its entire domain. Let's study the values the function takes to the left and to the right of the x-intercept.
To the left of the x-intercept on a line that slants up it is negative, and a line that slants down is positive. To the right of the x-intercept it is the other way around. A line that slants up is there is positive, whereas a line that slants down is negative. Let's summarize the differences in a table.
