Exploring the Domain: When is (49+2x)/(x+4) Defined?

Domain Restrictions with Rational Functions

Given the following function:

49+2xx+4 \frac{49+2x}{x+4}

Does the function have a domain? If so, what is it?

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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?
00:03 To find the domain, remember that division by 0 is not allowed
00:08 Therefore, let's find the solution that makes the denominator zero
00:12 Let's isolate X
00:17 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

Given the following function:

49+2xx+4 \frac{49+2x}{x+4}

Does the function have a domain? If so, what is it?

2

Step-by-step solution

To determine the domain of the function 49+2xx+4 \frac{49 + 2x}{x + 4} , we need to focus on avoiding division by zero, which occurs when the denominator is zero.

Let's identify the denominator of the function:

  • The denominator is x+4 x + 4 .

Next, we set the denominator equal to zero and solve for x x :

  • x+4=0 x + 4 = 0
  • Subtract 4 from both sides: x=4 x = -4

This calculation shows that the function is undefined when x=4 x = -4 . Thus, the domain of the function is all real numbers except x=4 x = -4 .

Therefore, the domain of the function is x4 x \neq -4 .

In terms of the provided choices, this corresponds to choice 4:

Yes, x4 x \ne -4

3

Final Answer

Yes, x4 x\ne-4

Key Points to Remember

Essential concepts to master this topic
  • Domain Rule: Function undefined when denominator equals zero
  • Technique: Set x + 4 = 0, solve to get x = -4
  • Check: Substitute x = -4: denominator becomes 0, confirming restriction ✓

Common Mistakes

Avoid these frequent errors
  • Setting the numerator equal to zero instead of denominator
    Don't set 49 + 2x = 0 to find domain restrictions = wrong excluded values! The numerator being zero creates zeros of the function, not domain restrictions. Always set only the denominator equal to zero to find where the function is undefined.

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 does the numerator not affect the domain?

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The numerator can equal zero without any problems - this just means the function value is 0. Only when the denominator equals zero do we get division by zero, which is undefined.

What does x ≠ -4 actually mean?

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It means x can be any real number except -4. So x can be -4.1, -3.9, 0, 100, but never exactly -4.

How do I write the domain in interval notation?

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The domain is (,4)(4,) (-\infty, -4) \cup (-4, \infty) . The parentheses around -4 show it's excluded from the domain.

What happens if I plug in x = -4?

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You get 49+2(4)4+4=410 \frac{49 + 2(-4)}{-4 + 4} = \frac{41}{0} , which is undefined. This confirms why x = -4 must be excluded from the domain.

Can a function have multiple domain restrictions?

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Yes! If the denominator factors into multiple terms, each factor set to zero gives a restriction. For example, 1(x2)(x+1) \frac{1}{(x-2)(x+1)} excludes both x = 2 and x = -1.

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