SAT Math : How to find f(x)

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #91 : How To Find F(X)

Two functions

Define  and  to be the functions graphed above. Evaluate 

.

Possible Answers:

The expression is not defined.

Correct answer:

The expression is not defined.

Explanation:

It can be seen below that a horizontal line can be drawn through two points of the graph of .

Hlt

 fails the Horizontal Line Test, which means that  has no inverse.  does not exist, so the expression  is undefined.

Example Question #92 : How To Find F(X)

Function 4

Define  as the function graphed above. Define function .

Evaluate .

Possible Answers:

3 is not in the domain of .

Correct answer:

Explanation:

.

As can be seen in the diagram below, .Function 4a

Therefore, 

, so

Example Question #93 : How To Find F(X)

Two functions

Define  and  to be the functions graphed above.

Evaluate 

Possible Answers:

4 is not in the domain of .

Correct answer:

Explanation:

.

From the diagram below, it can be seen that 

Two functions g 1

Therefore, .

From the diagram below, it can be seen that 

.

Two functions f

Therefore, the correct response is that .

Example Question #94 : How To Find F(X)

Two functions

Define  and  to be the functions graphed above. Evaluate 

Possible Answers:

 is undefined.

Correct answer:

Explanation:

.

From the diagram below, it can be seen that 

Two functions g 1

Therefore, .

From the diagram below, it can be seen that 

Two functions f

so, by definition,

.

Therefore, the correct response is that

.

Example Question #95 : How To Find F(X)

Function 4

Define  as the function graphed above. Define function .

Evaluate .

Possible Answers:

4 is outside the domain of 

Correct answer:

Explanation:

, so 

From the diagram below, we see that .

Function 4a

The correct response is that .

Example Question #96 : How To Find F(X)

Two functions

Define  and  to be the functions graphed above. For which of the following values of  is the statement 

a true statement?

Possible Answers:

The statement is not correct for any value of .

Correct answer:

Explanation:

or

This can be solved by graphing  and  on the same set of axes and noting their points of intersection:

Two functions together

The graphs of the two functions intersect at the point . Therefore, 

, and 

.

The correct response is .

Example Question #97 : How To Find F(X)

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,

From the diagram, we can see that

Therefore, to find the -intercepts of , set  equal to these numbers; equivalently, subtract 5 from each number. We get that

Therefore, the -intercepts of the graph of  are the points

.

The correct choice is .

Example Question #131 : 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 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

Therefore, , and the correct response is .

Example Question #99 : How To Find F(X)

Define a function  as follows:

, where the domain of  is the set .

Give the range of .

Possible Answers:

Correct answer:

Explanation:

This problem can be solved by examining the behavior of the graph of , which is a parabola.

Since the quadratic coefficient is 1, a positive number, its vertex is a minumum. The -coordinate of the vertex can be found by setting , and calculating:

The -coordinate is

The minimum value of  is therefore 1, and this occurs at . This makes 1 the lower bound of the range.

Since the graph of  is a parabola, it decreases everywhere for  and increases everywhere for . Therefore, we can evaluate  and , and choose the higher value as the maximum value on the given domain.

We choose 26 as the upper bound of the range.

Therefore, the range of , given the domain restriction, is the set .

Example Question #100 : How To Find F(X)

Possible Answers:

Correct answer:

Explanation:

The first step is to cross multiple which leaves you with .  The next step is to get all  on one side of the equation and all constants on the other.  You can add  to both sides then subtract  from both sides.  This gives us .  The last step is to get  by itself by dividing each side by  giving an answer of 

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