AP Calculus BC Flashcards: Removing Discontinuities

Study Removing Discontinuities in AP Calculus BC with focused flashcards that help you recognize the idea, recall the key rule, and apply it in practice-style prompts.

AP Calculus BC

Removing Discontinuities

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QUESTION
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What is the behavior of f(x)f(x) at a jump discontinuity?

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ANSWER

Differing left and right-hand limits. Left and right limits exist but are unequal.

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This deck focuses on Removing Discontinuities, giving you a quick way to review the definitions, rules, and examples that matter most for AP Calculus BC.

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Flashcard 1: What is the behavior of f(x)f(x) at a jump discontinuity?

Answer: Differing left and right-hand limits. Left and right limits exist but are unequal.

Flashcard 2: What is a jump discontinuity?

Answer: A discontinuity where a function has differing left and right limits at a point. The function 'jumps' from one value to another at the point.

Flashcard 3: Which discontinuity is present in f(x)=x21x1f(x) = \frac{x^2 - 1}{x - 1} at x=1x=1?

Answer: Removable. The factor (x1)(x-1) cancels, leaving a hole at x=1x=1.

Flashcard 4: What kind of discontinuity does f(x)=1xf(x) = \frac{1}{x} have at x=0x = 0?

Answer: Infinite discontinuity. Division by zero creates a vertical asymptote at x=0x=0.

Flashcard 5: What kind of discontinuity does f(x)=1xf(x) = \frac{1}{x} have at x=0x = 0?

Answer: Infinite discontinuity. Division by zero creates a vertical asymptote at x=0x=0.

Flashcard 6: Find the removable discontinuity in f(x)=x225x5f(x) = \frac{x^2 - 25}{x - 5}.

Answer: x=5x = 5. The denominator becomes zero when x=5x=5, creating a hole.

Flashcard 7: Determine the discontinuity type: f(x)=1xf(x) = \frac{1}{x} at x=0x = 0.

Answer: Infinite discontinuity. Division by zero with no cancellation creates a vertical asymptote.

Flashcard 8: Identify the discontinuity type: f(x)=x24x2f(x) = \frac{x^2 - 4}{x - 2} at x=2x = 2.

Answer: Removable discontinuity. The factor (x2)(x-2) cancels, creating a hole at x=2x=2.

Flashcard 9: Remove the discontinuity in f(x)=x24x2f(x) = \frac{x^2 - 4}{x - 2}.

Answer: Redefine f(2)=4f(2) = 4. The limit at x=2x=2 is 4, so define f(2)=4f(2)=4 for continuity.

Flashcard 10: What is the general approach to remove a discontinuity?

Answer: Simplify and redefine the function. Factor out common terms and define the function at the hole.

Flashcard 11: Identify the discontinuity at x=0x = 0 for f(x)=1x2f(x) = \frac{1}{x^2}.

Answer: Infinite discontinuity. Division by zero creates a vertical asymptote at x=0x=0.

Flashcard 12: What is the limit limx1x31x1\lim_{x \to 1} \frac{x^3 - 1}{x - 1}?

Answer:

  1. Factor: (x2+x+1)(x1)x1=x2+x+1\frac{(x^2+x+1)(x-1)}{x-1} = x^2+x+1, so limit is 3.

Flashcard 13: What is the limit definition of continuity at x=ax = a?

Answer: limxaf(x)=f(a)\lim_{x \to a} f(x) = f(a). The limit as xx approaches aa equals the function value.

Flashcard 14: Determine the discontinuity type: f(x)=1xf(x) = \frac{1}{x} at x=0x = 0.

Answer: Infinite discontinuity. Division by zero with no cancellation creates a vertical asymptote.

Flashcard 15: Find the removable discontinuity: f(x)=x29x3f(x) = \frac{x^2 - 9}{x - 3}.

Answer: x=3x = 3. The denominator equals zero when x=3x=3, creating a hole.

Flashcard 16: What is the behavior of f(x)f(x) at a jump discontinuity?

Answer: Differing left and right-hand limits. Left and right limits exist but are unequal.

Flashcard 17: State the condition for a function to have no discontinuities.

Answer: The function must be continuous everywhere in its domain. No holes, jumps, or vertical asymptotes anywhere.

Flashcard 18: What condition creates a removable discontinuity?

Answer: A factor cancels in the numerator and denominator. Common factors in numerator and denominator create holes.

Flashcard 19: What does it mean for a function to be continuous?

Answer: The function is continuous if it's defined and its limit equals the function value. Three conditions: defined, limit exists, and they're equal.

Flashcard 20: What is the limit as x2x \to 2 of x24x2\frac{x^2 - 4}{x - 2}?

Answer:

  1. Factor and cancel: (x+2)(x2)x2=x+2\frac{(x+2)(x-2)}{x-2} = x+2.

Flashcard 21: What is a removable discontinuity in a function?

Answer: A point where a function is not defined but can be redefined to make it continuous. The limit exists but doesn't equal the function value.

Flashcard 22: What is the limit as x3x \to 3 of x29x3\frac{x^2 - 9}{x - 3}?

Answer:

  1. Factor: (x+3)(x3)x3=x+3\frac{(x+3)(x-3)}{x-3} = x+3, so limit is 6.

Flashcard 23: Find the limit: limx2x24x2\lim_{x \to 2} \frac{x^2 - 4}{x - 2}.

Answer:

  1. Factor and cancel: (x+2)(x2)x2=x+2\frac{(x+2)(x-2)}{x-2} = x+2, so limit is 2+2=42+2=4.

Flashcard 24: What condition creates a removable discontinuity?

Answer: A factor cancels in the numerator and denominator. Common factors in numerator and denominator create holes.

Flashcard 25: Find and remove the discontinuity: f(x)=x24xx4f(x) = \frac{x^2 - 4x}{x - 4}.

Answer: Redefine f(4)=4f(4) = 4. Factor: x(x4)x4=x\frac{x(x-4)}{x-4} = x, so limit at x=4x=4 is 4.

Flashcard 26: What must be true for f(x)f(x) to be continuous at x=ax = a?

Answer: limxaf(x)=f(a)\lim_{x \to a} f(x) = f(a). All three continuity conditions must hold at the point.

Flashcard 27: Identify the removable discontinuity in f(x)=x24xx(x4)f(x) = \frac{x^2 - 4x}{x(x - 4)}.

Answer: x=0x = 0. The factor xx in denominator creates a hole when x=0x=0.

Flashcard 28: What is the necessary condition for a function to be continuous?

Answer: The function is defined and limits match the function value. Function exists, limit exists, and both values are equal.

Flashcard 29: How do you remove a removable discontinuity?

Answer: Redefine the function at the discontinuity point. Set the function value equal to the limit at that point.

Flashcard 30: How is a jump discontinuity characterized?

Answer: Differing left and right-hand limits. The function has different values approaching from each side.

Flashcard 31: Determine the discontinuity: f(x)=x24x2f(x) = \frac{x^2 - 4}{x - 2} at x=2x = 2.

Answer: Removable discontinuity. The factor (x2)(x-2) cancels, leaving a hole at x=2x=2.

Flashcard 32: State the condition for a function to have no discontinuities.

Answer: The function must be continuous everywhere in its domain. No holes, jumps, or vertical asymptotes anywhere.

Flashcard 33: What is the condition for a removable discontinuity?

Answer: A cancelable factor in the expression. A common factor exists in both numerator and denominator.

Flashcard 34: What is an infinite discontinuity?

Answer: A discontinuity where a function approaches infinity at a point. The function has a vertical asymptote at that point.

Flashcard 35: What is the limit of limx1x21x1\lim_{x \to 1} \frac{x^2 - 1}{x - 1}?

Answer:

  1. Factor: (x+1)(x1)x1=x+1\frac{(x+1)(x-1)}{x-1} = x+1, so limit is 1+1=21+1=2.

Flashcard 36: How do you remove a removable discontinuity?

Answer: Redefine the function at the discontinuity point. Set the function value equal to the limit at that point.

Flashcard 37: Which discontinuity is present in f(x)=x21x1f(x) = \frac{x^2 - 1}{x - 1} at x=1x=1?

Answer: Removable. The factor (x1)(x-1) cancels, leaving a hole at x=1x=1.

Flashcard 38: Identify and remove the discontinuity of f(x)=x29x3f(x) = \frac{x^2 - 9}{x - 3}.

Answer: Redefine f(3)=6f(3) = 6. Factor: (x+3)(x3)x3=x+3\frac{(x+3)(x-3)}{x-3} = x+3, so limit is 6.

Flashcard 39: Identify the discontinuity at x=0x = 0 for f(x)=1x2f(x) = \frac{1}{x^2}.

Answer: Infinite discontinuity. Division by zero creates a vertical asymptote at x=0x=0.

Flashcard 40: What happens to f(x)f(x) at an essential discontinuity?

Answer: The limits don't exist or are undefined. The function oscillates wildly or has no pattern near the point.

Flashcard 41: What is the limit limx1x31x1\lim_{x \to 1} \frac{x^3 - 1}{x - 1}?

Answer:

  1. Factor: (x2+x+1)(x1)x1=x2+x+1\frac{(x^2+x+1)(x-1)}{x-1} = x^2+x+1, so limit is 3.

Flashcard 42: Identify the discontinuity type: f(x)=x24x2f(x) = \frac{x^2 - 4}{x - 2} at x=2x = 2.

Answer: Removable discontinuity. The factor (x2)(x-2) cancels, creating a hole at x=2x=2.

Flashcard 43: What happens to f(x)f(x) at an essential discontinuity?

Answer: The limits don't exist or are undefined. The function oscillates wildly or has no pattern near the point.

Flashcard 44: What is the limit as x2x \to 2 of x24x2\frac{x^2 - 4}{x - 2}?

Answer:

  1. Factor and cancel: (x+2)(x2)x2=x+2\frac{(x+2)(x-2)}{x-2} = x+2.

Flashcard 45: What is the condition for a removable discontinuity?

Answer: A cancelable factor in the expression. A common factor exists in both numerator and denominator.

Flashcard 46: Find the limit: limx2x24x2\lim_{x \to 2} \frac{x^2 - 4}{x - 2}.

Answer:

  1. Factor and cancel: (x+2)(x2)x2=x+2\frac{(x+2)(x-2)}{x-2} = x+2, so limit is 2+2=42+2=4.

Flashcard 47: When is a discontinuity considered non-removable?

Answer: If limits do not exist or differ at a point. No common factors cancel or limits become infinite.

Flashcard 48: What is an infinite discontinuity?

Answer: A discontinuity where a function approaches infinity at a point. The function has a vertical asymptote at that point.

Flashcard 49: What must be true for f(x)f(x) to be continuous at x=ax = a?

Answer: limxaf(x)=f(a)\lim_{x \to a} f(x) = f(a). All three continuity conditions must hold at the point.

Flashcard 50: Identify the discontinuity type: f(x)=x21x1f(x) = \frac{x^2 - 1}{x - 1} at x=1x = 1.

Answer: Removable discontinuity. The factor (x1)(x-1) cancels, creating a hole at x=1x=1.

Flashcard 51: Identify the removable discontinuity in f(x)=x24xx(x4)f(x) = \frac{x^2 - 4x}{x(x - 4)}.

Answer: x=0x = 0. The factor xx in denominator creates a hole when x=0x=0.

Flashcard 52: What is the limit as x3x \to 3 of x29x3\frac{x^2 - 9}{x - 3}?

Answer:

  1. Factor: (x+3)(x3)x3=x+3\frac{(x+3)(x-3)}{x-3} = x+3, so limit is 6.

Flashcard 53: What type of discontinuity occurs at f(x)=1xf(x) = \frac{1}{x} at x=0x = 0?

Answer: Infinite discontinuity. Division by zero creates a vertical asymptote at x=0x=0.

Flashcard 54: When is a discontinuity considered non-removable?

Answer: If limits do not exist or differ at a point. No common factors cancel or limits become infinite.

Flashcard 55: What does limxaf(x)=\lim_{x \to a} f(x) = \infty imply about f(x)f(x) at x=ax = a?

Answer: Infinite discontinuity at x=ax = a. The function approaches infinity, creating a vertical asymptote.

Flashcard 56: What is the limit definition of continuity at x=ax = a?

Answer: limxaf(x)=f(a)\lim_{x \to a} f(x) = f(a). The limit as xx approaches aa equals the function value.

Flashcard 57: What is a jump discontinuity?

Answer: A discontinuity where a function has differing left and right limits at a point. The function 'jumps' from one value to another at the point.

Flashcard 58: What is the general approach to remove a discontinuity?

Answer: Simplify and redefine the function. Factor out common terms and define the function at the hole.

Flashcard 59: Remove the discontinuity in f(x)=x24x2f(x) = \frac{x^2 - 4}{x - 2}.

Answer: Redefine f(2)=4f(2) = 4. The limit at x=2x=2 is 4, so define f(2)=4f(2)=4 for continuity.

Flashcard 60: Find the removable discontinuity: f(x)=x29x3f(x) = \frac{x^2 - 9}{x - 3}.

Answer: x=3x = 3. The denominator equals zero when x=3x=3, creating a hole.

Flashcard 61: Identify and remove the discontinuity of f(x)=x29x3f(x) = \frac{x^2 - 9}{x - 3}.

Answer: Redefine f(3)=6f(3) = 6. Factor: (x+3)(x3)x3=x+3\frac{(x+3)(x-3)}{x-3} = x+3, so limit is 6.

Flashcard 62: What is the limit of limx1x21x1\lim_{x \to 1} \frac{x^2 - 1}{x - 1}?

Answer:

  1. Factor: (x+1)(x1)x1=x+1\frac{(x+1)(x-1)}{x-1} = x+1, so limit is 1+1=21+1=2.

Flashcard 63: Find and remove the discontinuity: f(x)=x24xx4f(x) = \frac{x^2 - 4x}{x - 4}.

Answer: Redefine f(4)=4f(4) = 4. Factor: x(x4)x4=x\frac{x(x-4)}{x-4} = x, so limit at x=4x=4 is 4.

Flashcard 64: Identify the discontinuity type: f(x)=x21x1f(x) = \frac{x^2 - 1}{x - 1} at x=1x = 1.

Answer: Removable discontinuity. The factor (x1)(x-1) cancels, creating a hole at x=1x=1.

Flashcard 65: What type of discontinuity occurs at f(x)=1xf(x) = \frac{1}{x} at x=0x = 0?

Answer: Infinite discontinuity. Division by zero creates a vertical asymptote at x=0x=0.

Flashcard 66: How is a jump discontinuity characterized?

Answer: Differing left and right-hand limits. The function has different values approaching from each side.

Flashcard 67: Determine the discontinuity: f(x)=x24x2f(x) = \frac{x^2 - 4}{x - 2} at x=2x = 2.

Answer: Removable discontinuity. The factor (x2)(x-2) cancels, leaving a hole at x=2x=2.

Flashcard 68: What does it mean for a function to be continuous?

Answer: The function is continuous if it's defined and its limit equals the function value. Three conditions: defined, limit exists, and they're equal.

Flashcard 69: What does limxaf(x)=\lim_{x \to a} f(x) = \infty imply about f(x)f(x) at x=ax = a?

Answer: Infinite discontinuity at x=ax = a. The function approaches infinity, creating a vertical asymptote.

Flashcard 70: What is a removable discontinuity in a function?

Answer: A point where a function is not defined but can be redefined to make it continuous. The limit exists but doesn't equal the function value.

Flashcard 71: What is the necessary condition for a function to be continuous?

Answer: The function is defined and limits match the function value. Function exists, limit exists, and both values are equal.

Flashcard 72: Find the removable discontinuity in f(x)=x225x5f(x) = \frac{x^2 - 25}{x - 5}.

Answer: x=5x = 5. The denominator becomes zero when x=5x=5, creating a hole.