Look at the function graphed below.
What are the areas of positivity and negativity of the function?
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Look at the function graphed below.
What are the areas of positivity and negativity of the function?
Let's remember that the function is positive when it is above the X-axis. The function is negative when it is below the X-axis.
Let's note that the intersection point of the graph with the X-axis is:
This means that when , it is below the X-axis and when , it is above the X-axis.
In other words, the function is positive when and the function is negative when .
Positive
Negative
Look at the function shown in the figure.
When is the function positive?
Look for where the graph crosses the x-axis! This is called the x-intercept. At , the function equals zero and changes sign.
Positive means the y-values are above zero (graph above x-axis). Negative means y-values are below zero (graph below x-axis).
Because for all x-values less than 3.5, the graph sits above the x-axis. This means all corresponding y-values are positive numbers.
At , the function equals zero (neither positive nor negative). This is the boundary point where the sign changes.
Yes! Pick any x-value in a region and check if the graph is above or below the x-axis there. For example, at the graph is above, so is positive.
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