Math Problem Statement

For the function f(x)=|x+4|, evaluate the left and right limits of f(x) as x approaches −4.

Solution

To evaluate the left and right limits of f(x)=x+4f(x) = |x + 4| as xx approaches 4-4, we need to consider the behavior of the function from both directions:

  1. Right-hand limit: As x4+x \to -4^+ (approaching -4 from the right), x+4x + 4 will be positive (since values greater than -4 will make x+4>0x + 4 > 0), so x+4=x+4|x + 4| = x + 4. Therefore, limx4+x+4=limx4+(x+4)=0.\lim_{x \to -4^+} |x + 4| = \lim_{x \to -4^+} (x + 4) = 0.

  2. Left-hand limit: As x4x \to -4^- (approaching -4 from the left), x+4x + 4 will be negative (since values less than -4 will make x+4<0x + 4 < 0), so x+4=(x+4)|x + 4| = -(x + 4). Therefore, limx4x+4=limx4(x+4)=0.\lim_{x \to -4^-} |x + 4| = \lim_{x \to -4^-} -(x + 4) = 0.

Thus, both the left-hand and right-hand limits of f(x)f(x) as x4x \to -4 are equal to 0.

Would you like further explanation or have any questions? Here are 5 related questions:

  1. What happens to the limit of f(x)=x3f(x) = |x - 3| as x3x \to 3?
  2. How does the absolute value affect the continuity of the function?
  3. Can a function with absolute values have a jump discontinuity?
  4. What is the general approach to finding limits of absolute value functions?
  5. How would you evaluate the limit of f(x)=xaf(x) = |x - a| as xx approaches aa?

Tip: When dealing with absolute value functions, always break them into cases based on whether the expression inside the absolute value is positive or negative.

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Math Problem Analysis

Mathematical Concepts

Limits
Absolute Value Functions

Formulas

|x + a| = x + a when x + a > 0
|x + a| = -(x + a) when x + a < 0

Theorems

Limit laws
Piecewise functions

Suitable Grade Level

Grades 9-11