Math Problem Statement

Let f(x) be a periodic function of x with period 3 and f(x) = |2x − 1| + x for

−1 < x ≤ 2. Sketch the graph of the curve y = f(x) in the interval [−3, 4]

Solution

To sketch the graph of y=f(x)y = f(x) for the interval [3,4][-3, 4], let's break it down step by step, keeping in mind that f(x)f(x) is a periodic function with a period of 3 and its definition over the interval 1<x2-1 < x \leq 2 is:

f(x)=2x1+xf(x) = |2x - 1| + x

Step 1: Analyze f(x)f(x) over 1<x2-1 < x \leq 2

Let's first compute the values of f(x)=2x1+xf(x) = |2x - 1| + x for key points in the interval 1<x2-1 < x \leq 2.

1.1: Break into two cases for 2x1|2x - 1|

  • For x12x \leq \frac{1}{2}, 2x102x - 1 \leq 0, so 2x1=(2x1)=12x|2x - 1| = -(2x - 1) = 1 - 2x.
  • For x>12x > \frac{1}{2}, 2x1>02x - 1 > 0, so 2x1=2x1|2x - 1| = 2x - 1.

Thus, we have two pieces:

  1. f(x)=(12x)+x=1xf(x) = (1 - 2x) + x = 1 - x for 1<x12-1 < x \leq \frac{1}{2}.
  2. f(x)=(2x1)+x=3x1f(x) = (2x - 1) + x = 3x - 1 for 12<x2\frac{1}{2} < x \leq 2.

Now let's find the values of f(x)f(x) at key points:

  • At x=1x = -1, the interval is open, so no value is defined here.
  • At x=0x = 0, f(0)=10=1f(0) = 1 - 0 = 1.
  • At x=12x = \frac{1}{2}, f(12)=112=12f\left( \frac{1}{2} \right) = 1 - \frac{1}{2} = \frac{1}{2}.
  • At x=1x = 1, f(1)=3(1)1=2f(1) = 3(1) - 1 = 2.
  • At x=2x = 2, f(2)=3(2)1=5f(2) = 3(2) - 1 = 5.

Step 2: Extend the function periodically

Since f(x)f(x) is periodic with a period of 3, this means we will repeat the pattern for intervals to the left and right of 1<x2-1 < x \leq 2. Specifically:

  • For 4<x1-4 < x \leq -1, f(x)=f(x+3)f(x) = f(x + 3).
  • For 2<x52 < x \leq 5, f(x)=f(x3)f(x) = f(x - 3).

Step 3: Calculate values for the extended intervals

3.1: For 4<x1-4 < x \leq -1

Since f(x)f(x) repeats every 3 units, calculate f(x)=f(x+3)f(x) = f(x + 3):

  • For x=3x = -3, f(3)=f(0)=1f(-3) = f(0) = 1.
  • For x=2x = -2, f(2)=f(1)=2f(-2) = f(1) = 2.
  • For x=1x = -1, not defined, since the interval is open at 1-1.

3.2: For 2<x52 < x \leq 5

Similarly, for 2<x52 < x \leq 5, we use f(x)=f(x3)f(x) = f(x - 3):

  • For x=3x = 3, f(3)=f(0)=1f(3) = f(0) = 1.
  • For x=4x = 4, f(4)=f(1)=2f(4) = f(1) = 2.

Step 4: Sketch the graph

  1. From 3x0-3 \leq x \leq 0, the graph repeats the behavior from 1<x2-1 < x \leq 2.
  2. From 0x30 \leq x \leq 3, use the defined values for f(x)=2x1+xf(x) = |2x - 1| + x.
  3. From 3x43 \leq x \leq 4, repeat the earlier values using periodicity.

Final Graph:

The graph will consist of repeating segments of a V-shaped curve with different slopes in each period.

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Math Problem Analysis

Mathematical Concepts

Piecewise Functions
Periodic Functions
Absolute Value

Formulas

f(x) = |2x - 1| + x
Periodicity: f(x + 3) = f(x)

Theorems

Periodicity Theorem
Absolute Value Function Properties

Suitable Grade Level

Grades 10-12