Analyzing the Fraction 8/(−2+x): Applications and Domain

Domain of Rational Functions with Linear Denominators

Identify the field of application of the following fraction:

82+x \frac{8}{-2+x}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the domain of substitution
00:03 Domain of substitution exists, to ensure we don't divide by 0
00:06 Meaning the denominator in the fraction must be different from 0
00:09 We will use this formula in our exercise
00:19 We will isolate X to find the domain of substitution
00:33 This is the domain of substitution
00:36 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

Identify the field of application of the following fraction:

82+x \frac{8}{-2+x}

2

Step-by-step solution

Let's examine the following expression:

82+x \frac{8}{-2+x}

As we know, the only restriction that applies to division is division by 0, given that no number can be divided into 0 parts. Hence division by 0 is undefined.

Therefore, when we talk about a fraction, where the dividend (the number being divided) is in the numerator, and the divisor (the number we divide by) is in the denominator, the restriction applies only to the denominator, which must be different from 0,

In the given expression:

82+x \frac{8}{-2+x}

As stated, the restriction applies to the fraction's denominator only,

Therefore, in order for the given expression (the fraction - in this case) to be defined, we require that the expression in its denominator - does not equal zero, in other words:

2+x0 -2+x\neq0

We will solve this inequality, which is a point inequality of first degree, in the same way we solve a first-degree equation, meaning - we isolate the variable on one side, by moving terms (and dividing both sides of the inequality by its coefficient if needed):

2+x0x2 -2+x\neq0 \\ \boxed{x\neq 2}

Therefore, the domain (definition domain) of the given expression is:

x2 x\neq 2

(This means that if we substitute any number different from 2 2 for x, the expression will remain well-defined),

Therefore, the correct answer is answer C.

Note:

In a general form - solving an inequality of this form, meaning, a non-graphical, but point inequality - that uses the \neq sign and not the inequality signs: ,>,<,,, ,>,\hspace{2pt}<,\hspace{2pt}\geq,\hspace{2pt}\leq,\hspace{2pt} is identical in every way to an equation and therefore is solved in the same way and all rules used to solve an equation of any type are identical for it as well.

3

Final Answer

x2 x\neq2

Key Points to Remember

Essential concepts to master this topic
  • Rule: The denominator of a fraction can never equal zero
  • Technique: Set -2+x ≠ 0, then solve to get x ≠ 2
  • Check: If x = 2, then denominator = -2+2 = 0 (undefined) ✓

Common Mistakes

Avoid these frequent errors
  • Focusing on the numerator instead of denominator
    Don't set the numerator equal to zero or restrict it = wrong domain! The numerator can be any value including zero. Always focus only on when the denominator equals zero to find restrictions.

Practice Quiz

Test your knowledge with interactive questions

\( 2x+\frac{6}{x}=18 \)

What is the domain of the above equation?

FAQ

Everything you need to know about this question

Why can't we divide by zero?

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Division by zero is undefined because you can't split something into zero parts! It's like asking 'how many groups of nothing can you make from 8 items?' - it doesn't make sense mathematically.

What does 'field of application' or 'domain' mean?

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The domain is all the x-values that make the expression work (be defined). For fractions, we exclude any x-value that makes the denominator equal zero.

How do I solve -2+x ≠ 0?

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Treat it like a regular equation! Add 2 to both sides: x0+2 x \neq 0 + 2 , so x2 x \neq 2 . The ≠ symbol just means 'not equal to'.

Can I rewrite the fraction differently?

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Yes! 82+x \frac{8}{-2+x} is the same as 8x2 \frac{8}{x-2} , but the restriction stays the same: x ≠ 2.

What happens if I substitute x = 2?

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You get 82+2=80 \frac{8}{-2+2} = \frac{8}{0} , which is undefined. Your calculator might show 'ERROR' or 'UNDEFINED' - this confirms x = 2 is not allowed!

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