# HiSET: Math : Estimate rate of change from a graph

## Example Questions

### Example Question #1 : Rate Of Change Of A Function

The graph of a function is given above, with the coordinates of two points on the curve shown. Use the coordinates given to approximate the rate of change of the function between the two points.

Explanation:

The rate of change between two points on a curve can be approximated by calculating the change between two points.

Let  be the coordinates of the first point and  be the coordinates of the second point. Then the formula giving approximate rate of change is:

Notice that the numerator is the overall change in y, and the denominator is the overall change in x.

The calculation for the problem proceeds as follows:

Let  be the first point and  be the second point. Substitute in the values from these coordinates:

Subtract to get the final answer:

Note that it does not matter which you assign to be the first point and which you assign to be the second, as it will lead to the same value due to negatives canceling out.

### Example Question #1 : Estimate Rate Of Change From A Graph

Above is the graph of a function . Estimate the rate of change of  on the interval

Explanation:

The rate of change of a function  on the interval  is equal to

.

Set . Refer to the graph of the function below:

The graph passes through  and .

. Thus,

,

the correct response.

### Example Question #1 : Rate Of Change Of A Function

Above is the graph of a function , which is defined and continuous on . The average rate of change of  on the interval  is 4. Estimate

Explanation:

The rate of change of a function  on the interval  is equal to

.

Set . Examine the figure below:

The graph passes through the point , so . Therefore,

and, substituting,

Solve for  using algebra:

,

the correct response.

### Example Question #1 : Estimate Rate Of Change From A Graph

Above is the graph of a function. The average rate of change of  over the interval  is . Which of these values comes closest to being a possible value of ?

Explanation:

The average rate of change of a function  on the interval  is equal to

.

Restated, it is the slope of the line that passes through  and .

To find the correct value of  that answers this question, it suffices to examine the line with slope  through  and find the point among those given that is closest to the line. This line falls 4 units for every 5 horizontal units, so the line looks like this:

The -coordinate of the point of intersection is closer to 2 than to any other of the values in the other four choices. This makes 2 the correct choice.