Algebra 1 : How to find the domain of a function

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #11 : How To Find The Domain Of A Function

What is the domain of the function?

Possible Answers:

Correct answer:

Explanation:

In order for the function to be real, the value inside of the square root must be greater than or equal to zero. The domain refers to the possible values of the independent variable (x-value) that allow this to be true.

For this term to be real, must be greater than or equal to zero.

Example Question #11 : How To Find The Domain Of A Function

Express the following in Set Builder Notation:

 

Possible Answers:

Correct answer:

Explanation:

and stands for OR in Set Builder Notation

Example Question #12 : How To Find The Domain Of A Function

Find the domain of:  

Possible Answers:

Correct answer:

Explanation:

The graph will open to the left.  The contents inside the square root cannot be negative.  

Set the inside equal to zero.

Any number greater than one-third will be invalid, but any number below will be the domain of this function.

The domain is:   

Example Question #12 : How To Find The Domain Of A Function

 

 

What is the domain of the the following function?

  

Possible Answers:

All real numbers.

More information is needed to determine the domain of this function.

Correct answer:

Explanation:

At  , there is a hole in this function:

At all other values of x, both positive and negative, this function will be defined.

 

 

Example Question #13 : How To Find The Domain Of A Function

Find the domain of the following function.

Possible Answers:

Correct answer:

Explanation:

To find the range, we first need to find the domain of the function. Then we will determine the range by finding the output values based on the domain.

  

First, we can factor out x from the denominator:

Since the function will be undefined when the denominator equals 0, we know that x=0 and x=1 are not in the domain of this function. We also know that this function is undefined for all negative number since the function includes a root of an even degree. The exponent under the square root does not change this, since cubing a negative number will still result in a negative number, as with any odd degreed exponent. 

So, this function is defined at all non-negative values except for 0 and 1.

 

 

 

Example Question #12 : How To Find The Domain Of A Function

Find the domain and range of the following set and specify whether it is a function

Possible Answers:

Domain: 4,3,7

Range: 2,7,3

Function?: yes

 

Domain: 2,7,3

Range: 4,3,7

Function?: no

Domain: 4,3,7

Range: 2,7,3

Function?: no

Domain: all real numbers

Range: all real numbers

Function?: yes

Domain: 2,7,3 

Range: 4,3,7

Function?: yes

Correct answer:

Domain: 4,3,7

Range: 2,7,3

Function?: no

Explanation:

The domain is defined as the input values or x values of a set.

So domain: 4,3,7

The range is defined as the output values or y values of a set.

So range: 2,7,3

In order for the set to be a function, each input value must have only one corresponding output value. In this example, the input value 4 has two output values: 2 and 3. The set is not a function.

 

Example Question #13 : How To Find The Domain Of A Function

What is the domain of the sets of ordered pairs?

 

Possible Answers:

 

Correct answer:

Explanation:

The domain of a set of ordered pairs is the  values.

The  values are the first number in each set of coordinates.

The  values are:

Example Question #16 : How To Find The Domain Of A Function

Find the domain of the function:

Possible Answers:

All real numbers

 and 

Correct answer:

 and 

Explanation:

The domain consists of all values that the input  can be without making the output  unreasonable. In our problem, the only condition that would dissatisfy the equations parameters is a negative inside the square root. However, having  inside the square root makes this a bit tricky, because we have to consider that squaring this value will always yield something positive. Thus, we cannot have any values of  whose squares are strictly less than . Thus, the domain must be all values of  that are greater than or equal to  and less than or equal to .

 

 

Example Question #18 : How To Find The Domain Of A Function

Find the domain of the following function:

Possible Answers:

All real numbers

Correct answer:

Explanation:

To solve this equation you must look at the denominator since the denominator can never equal zero.

You need to set the denominator equal to  then solve for .

,  then square root both sides to get

, the value that  cannot be, therefore, is .

Example Question #17 : How To Find The Domain Of A Function

State the domain and range of the following graph. Also specify whether it is a function or not.

Screen shot 2015 08 14 at 10.55.58 pm

Possible Answers:

Domain: y = all real numbers

Range: 

Function?: no

Domain: x = all real numbers

Range: 

Function?: yes

Domain: 

Range: y = all real numbers

Function?: yes

Domain: 

Range: y = all real numbers

Function?: no

Domain: x = all real numbers

Range:

Function?: no

Correct answer:

Domain: 

Range: y = all real numbers

Function?: no

Explanation:

The domain is defined as the input values or x values of a set. We can see that x is never less than zero

So domain: 0 ≤ x < ∞

The range is defined as the output values or y values of a set. We can see that we reach all values of y

So range: y = all real numbers

In order for the set to be a function, each input value must have only one corresponding output value. Another way of interpreting this graphically is that the graph must be able to pass the vertical line test. If we draw a vertical line on this graph, it corsses the parabola twice. This means there are multiple y output values for a single x input value.

Therefore, the graph is not a function

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