Domain of a Function: Finding the Domain of a Square Root Function

Examples with solutions for Domain of a Function: Finding the Domain of a Square Root Function

Exercise #1

Look at the following function:

2x+202x10 \frac{2x+20}{\sqrt{2x-10}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To determine the domain of the function 2x+202x10 \frac{2x+20}{\sqrt{2x-10}} , we must ensure that the expression under the square root is non-negative, because the square root of a negative number is not defined in the real numbers.

We start by analyzing the denominator, specifically the square root, 2x10\sqrt{2x-10}. For the square root to be valid (for real numbers), we require:

  • 2x100 2x-10 \geq 0

Now, solve the inequality 2x1002x - 10 \geq 0:

  • Add 10 to both sides: 2x102x \geq 10
  • Divide both sides by 2: x5x \geq 5

However, since the expression 2x102x-10 also prohibits zero in the denominator (as the square root in the denominator cannot be zero), we strictly have:

  • x>5x > 5

Thus, the domain of the function is all xx such that x>5x > 5.

Therefore, the domain of the function 2x+202x10\frac{2x+20}{\sqrt{2x-10}} is x>5 x > 5 .

Answer

x > 5

Exercise #2

Look at the following function:

23x \frac{23}{\sqrt{x}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To determine the domain of the function 23x \frac{23}{\sqrt{x}} , we must ensure the function is defined for all values in its domain. The expression involves a square root and a division.

  • First, consider the square root, x \sqrt{x} . This is only defined for x0 x \geq 0 . Therefore, initially, x x must be non-negative.

  • Second, because the square root is in the denominator of a fraction, x \sqrt{x} must not equal zero to avoid division by zero. Thus, x x must be strictly greater than 0.

Combining these conditions, we find that the domain of the function is x>0 x > 0 .

Therefore, the domain of the function is x>0 x > 0 , which corresponds to choice 3 from the provided options.

Answer

x > 0

Exercise #3

Look at the following function:

3x2 \frac{3}{\sqrt{x-2}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To determine the domain of the function 3x2 \frac{3}{\sqrt{x-2}} , we need to consider the constraints imposed by the square root and the fraction.

First, the expression inside the square root must be non-negative: x20 x - 2 \geq 0 . This simplifies to:

  • x2 x \geq 2

However, because the expression x2 \sqrt{x-2} is in the denominator of the fraction, we must also ensure that it is not equal to zero, as division by zero is undefined. Therefore, we have:

  • x20 x - 2 \neq 0

Solving this inequality gives:

  • x2 x \neq 2

Together, the solution to both conditions is that x x must be greater than 2 to ensure the function is defined. Thus, the domain of the function is:

x>2 x > 2

Therefore, the correct choice for the domain is x>2 x > 2 .

Answer

x > 2

Exercise #4

Look at the following function:

32x3 \frac{3}{\sqrt{2x-3}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To solve this problem, we need to determine the domain of the function given by 32x3 \frac{3}{\sqrt{2x-3}} . The fraction is undefined whenever the denominator is zero, and the square root requires the expression inside to be positive.

Let's break down the steps:

  • Since the square root is in the denominator, 2x3 2x - 3 must be strictly greater than zero.
  • Set up the inequality: 2x3>0 2x - 3 > 0 .
  • Solve the inequality for x x :
    • Add 3 to both sides: 2x>3 2x > 3 .
    • Divide both sides by 2: x>1.5 x > 1.5 .

The domain of the function is all real numbers x x such that x>1.5 x > 1.5 . Therefore, we write the domain as x>1.5 x > 1.5 .

Hence, the correct choice among the given options is: x>1.5 x > 1.5 which corresponds to choice number 3.

Answer

x > 1.5

Exercise #5

Look at the following function:

204x2 \frac{20}{\sqrt{4x-2}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To solve the problem of finding the domain of the function 204x2 \frac{20}{\sqrt{4x-2}} , we need to ensure that the expression under the square root is non-negative, and that we do not divide by zero.

**Step 1:** Solve for when the expression inside the square root is non-negative:

4x20 4x - 2 \geq 0

Add 2 to both sides:

4x2 4x \geq 2

Divide both sides by 4:

x0.5 x \geq 0.5

**Step 2:** Ensure the denominator is not zero:

4x20 4x - 2 \neq 0

From 4x2=0 4x - 2 = 0 , we solve:

4x=2 4x = 2

x=0.5 x = 0.5

Since at x=0.5 x = 0.5 , the denominator becomes zero, we exclude this point. Therefore, x > 0.5 .

Answer

x > 0.5

Exercise #6

Look at the following function:

4x+8 \frac{4}{\sqrt{x+8}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To solve this problem, we need to determine the domain of the function given by:

f(x)=4x+8 f(x) = \frac{4}{\sqrt{x+8}}

We must ensure that the function is defined for all x x . This involves considering the conditions under which the square root is valid and the denominator is non-zero.

Step 1: Analyze the square root expression x+8 \sqrt{x+8} . The expression inside the square root must be non-negative:

x+80 x + 8 \ge 0

Step 2: Solve the inequality:

  • Subtract 8 from both sides: x8 x \ge -8

Step 3: Consider the division by zero issue. The denominator x+8\sqrt{x+8} must be strictly greater than zero to avoid division by zero. Thus, we adjust the inequality to:

x+8>0 x + 8 > 0

Step 4: Solve the second inequality:

  • Subtract 8 from both sides: x>8 x > -8

Thus, the domain of the function is all x x such that x>8 x > -8 .

Review of the answer choices shows that the correct choice, consistent with our findings, is:

x>8 x > -8

Therefore, the domain of the function is x>8 x > -8 .

Answer

x > -8

Exercise #7

Look at the following function:

124x4 \frac{12}{\sqrt{4x-4}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To find the domain of the function 124x4 \frac{12}{\sqrt{4x-4}} , let's analyze the conditions necessary for the function to be defined.

The expression under the square root, 4x4 4x - 4 , must be positive, as the square root of a negative number is not defined in the real numbers, and division by zero is undefined. Therefore, we need:

  • 4x4>0 4x - 4 > 0

Solve this inequality step by step:

  • Add 4 to both sides: 4x4+4>0+4 4x - 4 + 4 > 0 + 4 , which simplifies to 4x>4 4x > 4 .
  • Divide both sides by 4: 4x4>44 \frac{4x}{4} > \frac{4}{4} , which simplifies to x>1 x > 1 .

The inequality x>1 x > 1 describes the domain of the function.

Therefore, the domain of the function 124x4 \frac{12}{\sqrt{4x-4}} is x>1 x > 1 .

Answer

x > 1

Exercise #8

Look at the following function:

2x+2x+2.5 \frac{2x+2}{\sqrt{x+2.5}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To find the domain of the function 2x+2x+2.5 \frac{2x+2}{\sqrt{x+2.5}} , we need to determine for which values of x x the expression is defined.

Step 1: Identify the restriction on the square root.
The square root function x+2.5 \sqrt{x+2.5} is defined when the expression inside the square root is non-negative. Thus, we have the inequality:

x+2.50 x + 2.5 \geq 0

Step 2: Solve the inequality for x x .
Subtract 2.5 from both sides:

x2.5 x \geq -2.5

Step 3: Ensure the denominator is not zero because division by zero is undefined.
Since x+2.50 x + 2.5 \neq 0 , we require:

x2.5 x \neq -2.5

Therefore, combining these results, the domain of the function is:

x>2.5 x > -2.5

The correct answer to the problem, represented as a choice, is:

x > -2.5

Answer

x > -\text{2}.5

Exercise #9

Look at the following function:

3x10 \frac{3}{\sqrt{x-10}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To find the domain of the function f(x)=3x10 f(x) = \frac{3}{\sqrt{x-10}} , follow these steps:

  • First, ensure the expression under the square root, x10 x-10 , is non-negative. This gives x100 x-10 \geq 0 , or equivalently, x10 x \geq 10 .
  • Second, the denominator of the function, x10\sqrt{x-10}, cannot be zero. This means x100 \sqrt{x-10} \neq 0 , leading to x100 x-10 \neq 0 . Therefore, x10 x \neq 10 .

Combining these conditions, the value of x x must satisfy x>10 x > 10 . This ensures both the definition of the square root and the non-zero nature of the denominator.

The correct domain of the function is x>10 x > 10 .

Answer

x > 10

Exercise #10

Look at the following function:

5x5 \frac{5}{\sqrt{x-5}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To determine the domain of the function 5x5 \frac{5}{\sqrt{x-5}} , we must ensure that the expression inside the square root, x5 x-5 , is positive. Furthermore, because the square root is in the denominator, x5 x-5 must be greater than zero:

  • Step 1: Set the argument of the square root greater than zero: x5>0 x-5 > 0 .
  • Step 2: Solve the inequality: Add 5 to both sides to get x>5 x > 5 .

Since the inequality x>5 x > 5 ensures that the denominator is neither zero nor negative, it defines the domain of the function. Thus, the function 5x5 \frac{5}{\sqrt{x-5}} is defined for all real numbers x x where x>5 x > 5 .

Therefore, the domain of the function is x>5 x > 5 .

Answer

x > 5

Exercise #11

Look at the following function:

3x+125x10 \frac{3x+12}{\sqrt{5x-10}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

The function given is 3x+125x10 \frac{3x+12}{\sqrt{5x-10}} .

To find the domain, we focus on the expression within the denominator's square root: 5x10 \sqrt{5x-10} .

The expression 5x10 5x-10 must be greater than 0 0 for the square root to be defined and the denominator to be non-zero.

Let's solve the inequality:

  • Set 5x10>0 5x-10 > 0 .
  • Add 10 10 to both sides: 5x>10 5x > 10 .
  • Divide both sides by 5 5 : x>2 x > 2 .

This means the domain of the function is all x x such that x>2 x > 2 .

The domain is, therefore, correctly expressed as x>2 x > 2 .

Answer

x > 2

Exercise #12

Look at the following function:

4x102.5x10 \frac{4x-10}{\sqrt{2.5x-10}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To find the domain of the function 4x102.5x10 \frac{4x-10}{\sqrt{2.5x-10}} , we need to ensure the expression under the square root is positive since it cannot equal zero or be negative.

Step 1: Set up the inequality based on the square root:

2.5x10>0 2.5x - 10 > 0

Step 2: Solve the inequality for x x :

  • Add 10 to both sides: 2.5x>10 2.5x > 10
  • Divide both sides by 2.5: x>102.5 x > \frac{10}{2.5}
  • Calculate: x>4 x > 4

Step 3: Interpret the result:

The domain of the function is all real numbers greater than 4, x>4 x > 4 , ensuring the expression inside the square root is always positive.

Thus, the correct domain is represented by choice 2: x>4 x > 4 .

Answer

x > 4

Exercise #13

Look at the following function:

2x+2x16 \frac{2x+2}{\sqrt{x-16}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To determine the domain of the function 2x+2x16 \frac{2x+2}{\sqrt{x-16}} , follow these steps:

  • Step 1: Identify the constraint imposed by the square root in the denominator.
  • Step 2: Solve the inequality x16>0 x-16 > 0 .
  • Step 3: Interpret the solution in terms of the domain.

Let's proceed:

Step 1: The function 2x+2x16 \frac{2x+2}{\sqrt{x-16}} has a square root in the denominator. For the square root to be defined in the real number system and prevent division by zero, the expression under the square root, x16 x-16 , must be greater than zero.

Step 2: Solve the inequality:

x16>0 x - 16 > 0

Add 16 to both sides:

x>16 x > 16

Step 3: The solution x>16 x > 16 means that the domain of the function is all real numbers greater than 16.

Therefore, the domain of the function is x>16 x > 16 , which corresponds to choice 2.

Answer

x > 16

Exercise #14

Look at the following function:

2x+22x8 \frac{2x+2}{\sqrt{2x-8}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To solve this problem, we need to determine where the function f(x)=2x+22x8 f(x) = \frac{2x+2}{\sqrt{2x-8}} is defined.

For the fraction to be defined, the denominator cannot be zero, and for the square root to be defined, the radicand (the expression inside the square root) must be non-negative.

Therefore, we need to solve the inequality:

2x80 2x - 8 \geq 0

Solving this inequality involves the following steps:

  • Add 8 to both sides: 2x8 2x \geq 8
  • Divide both sides by 2: x4 x \geq 4

However, if x=4 x = 4 , the expression inside the square root is zero, making the denominator zero and the overall expression undefined.

As a result, the domain of the function is x>4 x > 4 .

Therefore, the domain of the function is x>4 x > 4 .

Answer

x > 4

Exercise #15

Look at the following function:

x+7x7 \frac{x+7}{\sqrt{x-7}}

What is the domain of the function?

Video Solution

Step-by-Step Solution

To determine the domain of the function x+7x7\frac{x+7}{\sqrt{x-7}}, we need to ensure the denominator remains defined and non-zero. As follows:

First, focus on the denominator x7\sqrt{x-7}. The expression under the square root, x7x-7, must be greater than zero for the square root to be defined and not produce zero in the denominator:

  • x7>0x - 7 > 0

This simplifies to:

  • x>7x > 7

Since the expression under the square root must always be positive for this rational function to be defined, and x7\sqrt{x-7} in the denominator implies it cannot equal zero, our analysis is complete. Consequently, the domain of the function is the set of all xx such that:

The domain of the function is x>7x > 7.

Answer

x > 7

Exercise #16

(x3)(x+3)(x+3)(x3)=5 \sqrt{(x-3)(x+3)}\cdot\sqrt{(x+3)(x-3)}=-5

Video Solution

Answer

2 2