SAT Math : How to find f(x)

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #121 : Algebraic Functions

A jet goes from City 1 to City 2 at an average speed of 600 miles per hour, and returns along the same path at an average speed if 300 miles per hour. What is the average speed, in miles per hour, for the trip?

Possible Answers:

350miles/hour

300miles/hour

500miles/hour

450miles/hour

400miles/hour

Correct answer:

400miles/hour

Explanation:

Chose a number for the distance between City 1 and 2; 1800 works well, as it is a multiple of 600 and 300.

Now, find the time for each trip, the total distance, and the total time.

 

Now we can find the average speed by dividing the total distance by the total time.

Example Question #21 : How To Find F(X)

Find .

Possible Answers:

Correct answer:

Explanation:

Plug 5 into first:

Now, plug this answer into :

Example Question #21 : How To Find F(X)

If  and , what is ?

Possible Answers:

Correct answer:

Explanation:

Plug g(x) into f(x) as if it is just a variable. This gives f(g(x)) = 3(x– 12) + 7.

Distribute the 3: 3x– 36 + 7 = 3x– 29

Example Question #2821 : Sat Mathematics

Slide1

Some values of the function  are given in the table above.

For which of the following values of  does  equal 

Possible Answers:

Correct answer:

Explanation:

If  , then 

,

so  must be the correct choice. 

When we try the other values for b, our g(b) does not match.

We can verify by trying the other possible answer choices as follows.

And  is not a value on the table provided thus it is not a correct answer.

Example Question #121 : Algebraic Functions

f(x) = 4x + 17

Solve f(x) for the equation above for x = 3.

Possible Answers:

32

26

12

19

29

Correct answer:

29

Explanation:

The correct answer is 29. We plug in 3 into the equation above and solve for x. So we find that f(x) = 4(3) + 17. 12 + 17 = 29

Example Question #122 : Algebraic Functions

Define a function as follows:

.

If  and , evaluate .

Possible Answers:

Correct answer:

Explanation:

, so

 

Therefore, solve the equation

for :

Either or ; solve each.

, which we toss out:

 

, which we accept.

Example Question #123 : Algebraic Functions

Function 4

Define  to be the function graphed above.

Give the -intercept of the graph of the function , which is defined as

.

Possible Answers:

Correct answer:

Explanation:

The -intercept of a function is the point at which , so we can find this by evaluating .

From the diagram, it can be seen that , so

The -intercept of the graph of  is .

Example Question #124 : Algebraic Functions

Function 4

Define  to be the function graphed above.

Give the -intercept of the graph of the function , which is defined as

.

Possible Answers:

The correct answer is not given among the other four responses.

Correct answer:

The correct answer is not given among the other four responses.

Explanation:

The -intercept of a function is the point at which , so we can find this by evaluating .

From the diagram, it can be seen that , so , and the  -intercept of the graph of the function  is the point . This is not among the given responses.

Example Question #125 : Algebraic Functions

Function 4

Define  to be the function graphed above.

Which of the following is an -intercept of the graph of the function , if  is defined as

 ?

Possible Answers:

The graph of  has no -intercept.

Correct answer:

Explanation:

An -intercept of the graph of  has as its -coordinate a value such that

,

or, equivalently,

or

From the diagram below, it can be seen that if , then  or .

Function 4a

Therefore, the graph of  has two -intercepts,  and 

The correct choice is therefore .

Example Question #81 : How To Find F(X)

Function 4

Define  to be the function graphed above.

Give the -intercept of the graph of the function , which is defined as 

Possible Answers:

The graph of  has no -intercept.

Correct answer:

Explanation:

The -intercept of a function is the point at which , so we can find this by evaluating .

As can be seen in the diagram below, .

Function 4a

The -intercept is .

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