Math Problem Statement

Question 2

Sketch a function, f (x), that has all the given properties. The function must be continuous for all

x ∈ R, except at points in which the given properties force a discontinuity.

lim x→−2−

f (x) = 4, lim x→−2+ f (x) = −2, f (−2) = −3, limx→4 f (x) = −2, f (4) = 3

Solution

We need to sketch a function f(x)f(x) that meets the following requirements, including limits and a discontinuity:

  1. limx2f(x)=4\lim_{x \to -2^-} f(x) = 4 (the left-hand limit at x=2x = -2 is 4).
  2. limx2+f(x)=2\lim_{x \to -2^+} f(x) = -2 (the right-hand limit at x=2x = -2 is -2).
  3. f(2)=3f(-2) = -3 (the function value at x=2x = -2 is -3, not the same as either of the limits, which indicates a jump discontinuity at x=2x = -2).
  4. limx4f(x)=2\lim_{x \to 4} f(x) = -2 (the function approaches -2 as x4x \to 4).
  5. f(4)=3f(4) = 3 (the function value at x=4x = 4 is 3, indicating another discontinuity, but the limit and the function value are different).

Steps to construct the sketch:

  1. At x=2x = -2:

    • As x2x \to -2 from the left, f(x)f(x) approaches 4. This means as we approach x=2x = -2 from the left side, the function should be close to 4.
    • As x2x \to -2 from the right, f(x)f(x) approaches -2. The function should approach -2 from the right side of x=2x = -2.
    • At x=2x = -2, the function value is f(2)=3f(-2) = -3, which is neither 4 nor -2, creating a jump discontinuity at x=2x = -2. So, at x=2x = -2, we place a point at f(2)=3f(-2) = -3, and use open circles at 4 (left side) and -2 (right side) to indicate the limits.
  2. At x=4x = 4:

    • As x4x \to 4, f(x)f(x) approaches -2, meaning that as we get close to 4, the function should get close to -2. But the actual function value at x=4x = 4 is f(4)=3f(4) = 3, indicating another discontinuity at x=4x = 4. So, place a point at f(4)=3f(4) = 3, and an open circle at f(x)=2f(x) = -2 to represent the limit.
  3. Continuous behavior elsewhere:

    • Between these two discontinuities at x=2x = -2 and x=4x = 4, the function must be continuous (no jumps or breaks in the curve), but the specific shape of the curve can vary. It can smoothly connect the required limits and values. A possible simple connection could be a linear or smooth curve transitioning between these points.

Description of the sketch:

  • From x2x \to -2^-, the function approaches 4.
  • From x2+x \to -2^+, the function approaches -2.
  • At x=2x = -2, the function is f(2)=3f(-2) = -3, indicating a jump.
  • From x4x \to 4, the function approaches -2.
  • At x=4x = 4, the function is f(4)=3f(4) = 3, again indicating a discontinuity.

Would you like to see a sketch of this function?


Related Questions:

  1. How does the behavior of limits create discontinuities in a function?
  2. What is the difference between a removable discontinuity and a jump discontinuity?
  3. Can a function be continuous at a point where its limit exists but differs from the function value?
  4. How do left-hand and right-hand limits affect the continuity of a function?
  5. What are some other examples of functions with jump discontinuities?

Tip:

When graphing functions with discontinuities, always pay attention to open and closed circles, which indicate where the function has limits versus actual function values.

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Math Problem Analysis

Mathematical Concepts

Limits
Continuity
Discontinuities
Jump Discontinuity

Formulas

Limit properties: lim x→a f(x)
Discontinuity definitions

Theorems

Definition of limits
Continuity and discontinuity at a point

Suitable Grade Level

Grades 10-12