3 7 Skills Practice Piecewise And Step Functions Answers

Mastering Piecewise and Step Functions: 37 Skill-Building Practice Problems with Detailed Answers

Piecewise and step functions are fundamental concepts in algebra and precalculus that model real-world situations where rules change based on input values. Now, unlike single-formula functions, these functions use different expressions over specific intervals, making them powerful tools for describing everything from shipping costs to tax brackets. This guide provides 37 targeted practice problems, complete with step-by-step answers, to build fluency in interpreting, graphing, and solving these essential function types.

Understanding the Foundations: What Are Piecewise and Step Functions?

A piecewise function is defined by multiple sub-functions, each applying to a certain interval of the main function's domain. It is written using a large curly brace with conditions listed. For example: f(x) = { x² if x < 0 { 2x + 1 if x ≥ 0

A step function is a specific type of piecewise function where the output is constant over each interval, creating a graph that resembles steps. The most famous example is the greatest integer function, or floor function, f(x) = ⌊x⌋, which returns the greatest integer less than or equal to x.

The key skill is evaluating the function by first determining which condition the input satisfies, then applying the corresponding formula. Graphing requires plotting each piece on its interval, paying close attention to open or closed circles at boundary points to indicate inclusion or exclusion.

Practice Set 1: Basic Evaluation and Interpretation (Problems 1-10)

Problem 1: Given g(x) = { 3x - 2 if x ≤ 1 { x² + 1 if x > 1 Find g(0), g(1), and g(2).

Answer:

• g(0): 0 ≤ 1, so use 3x - 2. g(0) = 3(0) - 2 = -2.
• g(1): 1 ≤ 1, so use 3x - 2. g(1) = 3(1) - 2 = 1.
• g(2): 2 > 1, so use x² + 1. g(2) = (2)² + 1 = 5.

Problem 2: Evaluate h(x) = { -x if x < -2 { 5 if -2 ≤ x ≤ 3 { √x if x > 3 for h(-3), h(-2), h(4).

Answer:

• h(-3): -3 < -2, so use -x. h(-3) = -(-3) = 3.
• h(-2): -2 ≤ x ≤ 3 is true, so use 5. h(-2) = 5.
• h(4): 4 > 3, so use √x. h(4) = √4 = 2.

Problem 3: Let f(x) = ⌊x⌋ (the greatest integer function). Find f(2.7), f(-1.3), f(5).

Answer:

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• f(2.7): The greatest integer ≤ 2.7 is 2.
• f(-1.3): The greatest integer ≤ -1.3 is -2 (since -2 < -1.3 < -1).
• f(5): The greatest integer ≤ 5 is 5.

Problem 4: A shipping company charges: $5 for the first pound, $3 for each additional pound or fraction thereof. Model this with a step function C(w) for weight w > 0. Find C(1.2) and C(3.0).

Answer: The cost increases at each whole pound mark. C(w) = 5 + 3⌊w⌋ for w > 0? Let's test: For w=1, ⌊1⌋=1, C=5+3(1)=8, but it should be $5. Correction: The first pound is $5, so additional pounds start after 1. C(w) = 5 + 3⌊w - 1⌋ for w > 0? For w=1.2, ⌊0.2⌋=0, C=5. Correct. For w=3.0, ⌊2.0⌋=2, C=5+6=11. So C(w) = 5 + 3⌊w - 1⌋.

• C(1.2) = 5 + 3⌊0.2⌋ = 5 + 3(0) = $5.
• C(3.0) = 5 + 3⌊2.0⌋ = 5 + 3(2) = $11.

Problem 5: Evaluate p(x) = { 2 if x < -4 { 0 if -4 ≤ x < 2 { -2 if x ≥ 2 for p(-5), p(-4), p(2), p(10).

Answer:

• p(-5): -5 < -4 → 2.
• p(-4): -4 ≤ x < 2 is true → 0.
• p(2): x ≥ 2 is true → -2.
• p(10): x ≥ 2 → -2.

Problem 6: Given q(x) = { x+4 if x ≤ -1 { 2 if -1 < x ≤ 3 { 4 - x if x > 3 Find q(-1) and q(3).

Answer:

• q(-1): x ≤ -1 is true → use x+4. q(-1) = -1 + 4 = 3.
• q(3): -1 < x ≤ 3 is true → use 2. q(3) = 2.

Problem 7: For r(x) = ⌊2x⌋, find r(1.1), r(1.5), r(-0.7).

Answer:

• r(1.1) = ⌊2.2⌋ = 2.
• r(1.5) = ⌊3.0⌋ = 3.
• r(-0.7) = ⌊-1.4⌋ = -2 (greatest integer ≤ -1.4).

Problem 8: A parking garage charges $2 for the first hour and $1 for each additional hour or part thereof. Write a step function P(t) for time t in hours (t > 0). Find P(0.5) and P(2.1).

Answer: First hour is $2. Additional hours start after 1. P(t) = 2 + 1⌊t - 1⌋ for t > 0? For t=0.5, ⌊-0.5⌋=-1, P=1. Wrong. Need to handle t ≤ 1 separately. Better: