Math Problem Statement

which of the following is true: lim x 2- (8-x^3)^1/2 =0 limx2+ (8-x^3)^1/2=0 lim x 2 (8-x^3)^1/2 =0 or lim x 2- (8-x^3)^1/2 = limx2+ (8-x^3)^1/2=0

Solution

Let's analyze the given limits involving the function f(x)=8x3f(x) = \sqrt{8 - x^3} as xx approaches 2 from both sides.

1. Left-hand limit limx28x3\lim_{x \to 2^-} \sqrt{8 - x^3}:

As x2x \to 2^-, we substitute values slightly less than 2 into the function f(x)=8x3f(x) = \sqrt{8 - x^3}. When x=2x = 2, the expression becomes:

823=88=0\sqrt{8 - 2^3} = \sqrt{8 - 8} = 0

Now, for values of xx just less than 2 (like 1.999), 8x38 - x^3 will still be slightly positive because x3x^3 will be slightly less than 8, resulting in a positive square root close to 0. Thus:

limx28x3=0\lim_{x \to 2^-} \sqrt{8 - x^3} = 0

2. Right-hand limit limx2+8x3\lim_{x \to 2^+} \sqrt{8 - x^3}:

Similarly, as x2+x \to 2^+, we substitute values slightly greater than 2 into f(x)=8x3f(x) = \sqrt{8 - x^3}. However, for values of xx just greater than 2 (like 2.001), x3x^3 will be slightly greater than 8, making 8x38 - x^3 negative.

Since the square root of a negative number is not defined in the real number system, the function f(x)=8x3f(x) = \sqrt{8 - x^3} becomes undefined as x2+x \to 2^+.

Thus:

limx2+8x3is undefined.\lim_{x \to 2^+} \sqrt{8 - x^3} \quad \text{is undefined}.

3. Overall limit limx28x3\lim_{x \to 2} \sqrt{8 - x^3}:

Since the right-hand limit does not exist in the real number system, the overall limit does not exist. A limit only exists if both the left-hand and right-hand limits exist and are equal.

Conclusion:

  • limx28x3=0\lim_{x \to 2^-} \sqrt{8 - x^3} = 0
  • limx2+8x3\lim_{x \to 2^+} \sqrt{8 - x^3} does not exist (undefined)
  • Therefore, the overall limit limx28x3\lim_{x \to 2} \sqrt{8 - x^3} does not exist.

Hence, the correct answer is:

limx28x3=0\lim_{x \to 2^-} \sqrt{8 - x^3} = 0

Would you like more details on the process? Here are some additional related questions for practice:

  1. What happens to the function f(x)=8x3f(x) = \sqrt{8 - x^3} as x3x \to 3?
  2. How do we handle square roots of negative values in complex numbers?
  3. What is the definition of a two-sided limit?
  4. What does it mean for a function to be undefined at a point?
  5. How do we compute limits involving piecewise functions?

Tip: Always check both the left-hand and right-hand limits when dealing with limits to ensure they match for the overall limit to exist.

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Math Problem Analysis

Mathematical Concepts

Limits
Square Roots
One-Sided Limits
Real Numbers

Formulas

lim x → 2^- √(8 - x^3)
lim x → 2^+ √(8 - x^3)

Theorems

Limit of a Function
One-Sided Limits Theorem
Square Root Function

Suitable Grade Level

Grades 11-12