All SAT II Math I Resources
Example Questions
Example Question #1 : Graphing Exponential Functions
Give the -intercept of the graph of the equation .
The graph has no -intercept.
The graph has no -intercept.
Set and solve for
We need not work further. It is impossible to raise a positive number 2 to any real power to obtain a negative number. Therefore, the equation has no solution, and the graph of has no -intercept.
Example Question #21 : Solving Exponential Functions
What is/are the asymptote(s) of the graph of the function ?
and
An exponential function of the form
has as its one and only asymptote the horizontal line .
Since we define as
,
then ,
and the only asymptote is the line of the equation .
Example Question #1 : Graphing Exponential Functions
Determine whether each function represents exponential decay or growth.
a) growth
b) decay
a) decay
b) decay
a) decay
b) growth
a) growth
b) growth
a) decay
b) growth
a)
This is exponential decay since the base, , is between and .
b)
This is exponential growth since the base, , is greater than .
Example Question #4 : Graphing Exponential Functions
Match each function with its graph.
1.
2.
3.
a.
b.
c.
1.
2.
3.
1.
2.
3.
1.
2.
3.
1.
2.
3.
1.
2.
3.
For , our base is greater than so we have exponential growth, meaning the function is increasing. Also, when , we know that since . The only graph that fits these conditions is .
For , we have exponential growth again but when , . This is shown on graph .
For , we have exponential decay so the graph must be decreasing. Also, when , . This is shown on graph .
Example Question #71 : Functions And Graphs
An exponential funtion is graphed on the figure below to model some data that shows exponential decay. At , is at half of its initial value (value when ). Find the exponential equation of the form that fits the data in the graph, i.e. find the constants and .
To determine the constant , we look at the graph to find the initial value of , (when ) and find it to be . We can then plug this into our equation and we get . Since , we find that .
To find , we use the fact that when , is one half of the initial value . Plugging this into our equation with now known gives us . To solve for , we make use the fact that the natural log is the inverse function of , so that
.
We can write our equation as and take the natural log of both sides to get:
or .
Then .
Our model equation is .
Example Question #6 : Graphing Exponential Functions
In 2010, the population of trout in a lake was 416. It has increased to 521 in 2015.
Write an exponential function of the form that could be used to model the fish population of the lake. Write the function in terms of , the number of years since 2010.
We need to determine the constants and . Since in 2010 (when ), then and
To get , we find that when , . Then .
Using a calculator, , so .
Then our model equation for the fish population is
Example Question #361 : Sat Subject Test In Math I
What is the -intercept of the graph ?
The -intercept of any graph describes the -value of the point on the graph with a -value of .
Thus, to find the -intercept substitute .
In this case, you will get,
.
Example Question #2 : Graph Exponential Functions
What is the -intercept of ?
There is no -intercept.
The -intercept of a graph is the point on the graph where the -value is .
Thus, to find the -intercept, substitute and solve for .
Thus, we get:
Example Question #9 : Graphing Exponential Functions
What is the -intercept of ?
The -intercept of any function describes the point where .
Substituting this in to our funciton, we get:
Example Question #21 : Solving Exponential Functions
Which of the following functions represents exponential decay?
Exponential decay describes a function that decreases by a factor every time increases by .
These can be recognizable by those functions with a base which is between and .
The general equation for exponential decay is,
where the base is represented by and .
Thus, we are looking for a fractional base.
The only function that has a fractional base is,
.
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