Find the Domain: Understanding 8/(x - 2.5)

Rational Function Domains with Mixed Numbers

Given the following function:

8x212 \frac{8}{x-2\frac{1}{2}}

What is the domain of the function?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:07 Does the function have a domain? If it does, let's figure out what it is.
00:13 To find the domain, remember: division by zero is not allowed.
00:18 So, let's find the value that makes the denominator zero.
00:24 We'll need to isolate X to solve this.
00:28 And that's the solution to our question!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given the following function:

8x212 \frac{8}{x-2\frac{1}{2}}

What is the domain of the function?

2

Step-by-step solution

To determine the domain of the function 8x212 \frac{8}{x - 2\frac{1}{2}} , we'll follow these steps:

  • Step 1: Identify where the denominator is zero.

  • Step 2: Solve for x x in this scenario to find exclusions from the domain.

  • Step 3: Provide the domain, excluding these x x values.

Let's go through the problem step by step:
Step 1: We note that the function is undefined where the denominator equals zero.
Thus, set the denominator equal to zero: x212=0 \begin{aligned} x - 2\frac{1}{2} &= 0 \end{aligned}
Step 2: Solve for x x : x=212 \begin{aligned} x &= 2\frac{1}{2} \end{aligned}
Step 3: The domain of the function is all real numbers except 212 2\frac{1}{2} .
Therefore, we express the domain as all real numbers x x such that x212 x \ne 2\frac{1}{2} .

Thus, the solution to the problem is x212 x \ne 2\frac{1}{2} .

3

Final Answer

x212 x\ne2\frac{1}{2}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Rational functions are undefined when their denominators equal zero
  • Technique: Set x - 2½ = 0, so x = 2½
  • Check: Substitute excluded value: 8/(2½ - 2½) = 8/0 = undefined ✓

Common Mistakes

Avoid these frequent errors
  • Confusing the sign when finding domain exclusions
    Don't solve x - 2½ = 0 as x = -2½! This gives the wrong excluded value because you flipped the sign incorrectly. Always solve the denominator equation carefully: x - 2½ = 0 means x = 2½.

Practice Quiz

Test your knowledge with interactive questions

\( 22(\frac{2}{x}-1)=30 \)

What is the domain of the equation above?

FAQ

Everything you need to know about this question

Why can't the denominator be zero?

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Division by zero is undefined in mathematics! When the denominator equals zero, the function has no value at that point, so we must exclude it from the domain.

How do I write 2½ as an improper fraction?

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Convert the mixed number: 212=52 2\frac{1}{2} = \frac{5}{2} . Both forms are correct for expressing the excluded value!

What does 'domain' actually mean?

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The domain is the set of all possible x-values you can input into a function. It's like asking 'what numbers am I allowed to use?'

Is there a difference between x ≠ 2½ and x ≠ 5/2?

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No difference at all! 212 2\frac{1}{2} and 52 \frac{5}{2} are the same number, just written in different forms. Both mean x cannot equal 2.5.

What if there were multiple fractions in the denominator?

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Set the entire denominator equal to zero and solve. For example, if the denominator was (x-1)(x+3), you'd need both x ≠ 1 and x ≠ -3.

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