Math Problem Statement

lim (x -> 2^+) of (x^2 - 2x) / (floor(x) - x)

Solution

The given limit problem is:

limx2+x22xxx\lim_{x \to 2^+} \frac{x^2 - 2x}{\lfloor x \rfloor - x}

Key aspects:

  • x\lfloor x \rfloor represents the floor function, which gives the greatest integer less than or equal to xx.
  • We are approaching x=2x = 2 from the right (x2+x \to 2^+), so xx is slightly greater than 2.

Analyzing the limit:

  1. As x2+x \to 2^+, x=2\lfloor x \rfloor = 2, because the floor of any number slightly greater than 2 is still 2.

  2. Let's now examine the numerator: x22x=x(x2)x^2 - 2x = x(x - 2) As x2x \to 2, x22x0x^2 - 2x \to 0.

  3. The denominator: xx=2x\lfloor x \rfloor - x = 2 - x As x2+x \to 2^+, 2x02 - x \to 0^-, meaning the denominator is approaching zero from the negative side.

Thus, as x2+x \to 2^+, we have a 0/0 form, which suggests that we can apply L'Hôpital's Rule to evaluate the limit.

Applying L'Hôpital's Rule:

  1. Differentiate the numerator: ddx(x22x)=2x2\frac{d}{dx}(x^2 - 2x) = 2x - 2

  2. Differentiate the denominator: ddx(2x)=1\frac{d}{dx}(2 - x) = -1

  3. Now, applying L'Hôpital's Rule: limx2+2x21=limx2+(2x2)\lim_{x \to 2^+} \frac{2x - 2}{-1} = \lim_{x \to 2^+} -(2x - 2) Substituting x=2x = 2: (2(2)2)=(42)=2-(2(2) - 2) = -(4 - 2) = -2

Final result:

limx2+x22xxx=2\lim_{x \to 2^+} \frac{x^2 - 2x}{\lfloor x \rfloor - x} = -2

Would you like a detailed explanation of L'Hôpital's Rule or any other clarifications?

Here are some related questions to deepen your understanding:

  1. How does L'Hôpital's Rule work for indeterminate forms?
  2. What happens if the limit approaches from the left, x2x \to 2^-?
  3. How does the floor function affect limits in general?
  4. Can you think of other situations where the 0/0 indeterminate form occurs?
  5. What other methods besides L'Hôpital’s Rule can be used to evaluate limits?

Tip: Always check for indeterminate forms before applying L'Hôpital's Rule to ensure it is applicable.

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Math Problem Analysis

Mathematical Concepts

Limits
Floor Function
L'Hôpital's Rule

Formulas

x^2 - 2x
floor(x) - x
L'Hôpital's Rule: lim f(x)/g(x) = lim f'(x)/g'(x)

Theorems

L'Hôpital's Rule

Suitable Grade Level

Grades 11-12 (Advanced Calculus)