Examine the Domain of (2x+20)/√(2x-10)

Function Domain with Square Root Restrictions

Look at the following function:

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

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
00:00 Does the function have a domain? If so, what is it?
00:04 Root must be for a positive number greater than 0
00:09 Let's isolate X
00:23 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Look at the following function:

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

What is the domain of the function?

2

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 .

3

Final Answer

x>5 x > 5

Key Points to Remember

Essential concepts to master this topic
  • Rule: Square root expressions require non-negative values inside
  • Technique: Solve 2x - 10 > 0 to get x > 5
  • Check: Test x = 6: √(2(6) - 10) = √2 works ✓

Common Mistakes

Avoid these frequent errors
  • Including x = 5 in the domain
    Don't write x ≥ 5 when the square root is in the denominator = division by zero! When x = 5, we get √0 = 0 in the denominator, which makes the function undefined. Always exclude values that make the denominator zero.

Practice Quiz

Test your knowledge with interactive questions

\( \frac{6}{x+5}=1 \)

What is the field of application of the equation?

FAQ

Everything you need to know about this question

Why can't x equal 5 if the square root of 0 exists?

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While 0=0 \sqrt{0} = 0 exists, having zero in the denominator makes the entire fraction undefined. Division by zero is never allowed in mathematics!

What's the difference between x ≥ 5 and x > 5?

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x ≥ 5 includes x = 5, but x > 5 excludes it. Since our square root is in the denominator, we must use the strict inequality x > 5 to avoid division by zero.

Do I need to worry about the numerator 2x + 20?

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No! The numerator can be any real number. We only need to check the denominator for restrictions since division by zero is undefined, and square roots of negative numbers aren't real.

How do I check if x = 6 works in the domain?

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Substitute: 2(6)+202(6)10=322 \frac{2(6)+20}{\sqrt{2(6)-10}} = \frac{32}{\sqrt{2}} . Since 2>0 \sqrt{2} > 0 , this gives us a real number, so x = 6 is valid!

What if I have trouble solving 2x - 10 > 0?

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  • Add 10 to both sides: 2x > 10
  • Divide by 2: x > 5
  • Remember: when dividing by a positive number, the inequality direction stays the same!

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