Math Problem Statement

Write f(x) = [5−2x] as piecewise function. Note that [5 - 2x] is a floor function

Solution

The floor function 52x\lfloor 5 - 2x \rfloor gives the greatest integer less than or equal to 52x5 - 2x. To express f(x)=52xf(x) = \lfloor 5 - 2x \rfloor as a piecewise function, we need to break it down into intervals where the value of 52x5 - 2x lies between successive integers, as the floor function will output a constant integer on each such interval.

We examine intervals where 52x5 - 2x takes integer values:

  1. For 52x[n,n+1)5 - 2x \in [n, n+1), where nn is an integer, 52x=n\lfloor 5 - 2x \rfloor = n.

Let’s find the intervals by solving for xx in terms of 52x=n5 - 2x = n.

1. When 52x[4,5)5 - 2x \in [4, 5), then 52x=4\lfloor 5 - 2x \rfloor = 4:

452x<54 \leq 5 - 2x < 5 Solving for xx: 452x    x124 \leq 5 - 2x \implies x \leq \frac{1}{2} 52x<5    x>05 - 2x < 5 \implies x > 0 Thus, for 0<x120 < x \leq \frac{1}{2}, f(x)=4f(x) = 4.

2. When 52x[3,4)5 - 2x \in [3, 4), then 52x=3\lfloor 5 - 2x \rfloor = 3:

352x<43 \leq 5 - 2x < 4 Solving for xx: 352x    x123 \leq 5 - 2x \implies x \geq \frac{1}{2} 52x<4    x<15 - 2x < 4 \implies x < 1 Thus, for 12x<1\frac{1}{2} \leq x < 1, f(x)=3f(x) = 3.

3. When 52x[2,3)5 - 2x \in [2, 3), then 52x=2\lfloor 5 - 2x \rfloor = 2:

252x<32 \leq 5 - 2x < 3 Solving for xx: 252x    x12 \leq 5 - 2x \implies x \geq 1 52x<3    x<325 - 2x < 3 \implies x < \frac{3}{2} Thus, for 1x<321 \leq x < \frac{3}{2}, f(x)=2f(x) = 2.

4. When 52x[1,2)5 - 2x \in [1, 2), then 52x=1\lfloor 5 - 2x \rfloor = 1:

152x<21 \leq 5 - 2x < 2 Solving for xx: 152x    x321 \leq 5 - 2x \implies x \geq \frac{3}{2} 52x<2    x<25 - 2x < 2 \implies x < 2 Thus, for 32x<2\frac{3}{2} \leq x < 2, f(x)=1f(x) = 1.

5. When 52x[0,1)5 - 2x \in [0, 1), then 52x=0\lfloor 5 - 2x \rfloor = 0:

052x<10 \leq 5 - 2x < 1 Solving for xx: 052x    x20 \leq 5 - 2x \implies x \geq 2 52x<1    x<525 - 2x < 1 \implies x < \frac{5}{2} Thus, for 2x<522 \leq x < \frac{5}{2}, f(x)=0f(x) = 0.

This process can be continued for negative integers, covering the entire real line.

The piecewise function for f(x)=52xf(x) = \lfloor 5 - 2x \rfloor is therefore:

\begin{cases} 4, & 0 < x \leq \frac{1}{2} \\ 3, & \frac{1}{2} < x \leq 1 \\ 2, & 1 < x \leq \frac{3}{2} \\ 1, & \frac{3}{2} < x \leq 2 \\ 0, & 2 < x \leq 3 \end{cases}$$ Would you like further clarification or details on a specific part? Here are 5 related questions you might find interesting: 1. How does the behavior of a floor function differ from a ceiling function? 2. Can a piecewise function involve non-integer values for floor functions? 3. How would the piecewise function change if it were $$\lceil 5 - 2x \rceil$$ instead? 4. How can we express the floor function for more complex functions like $$\lfloor x^2 - 3x \rfloor$$? 5. How does the floor function behave as $$x$$ approaches infinity? **Tip**: The floor function can be a useful tool for simplifying expressions where rounding down to the nearest integer is required.

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Math Problem Analysis

Mathematical Concepts

Piecewise Functions
Floor Function
Inequalities
Interval Notation

Formulas

f(x) = ⌊5 - 2x⌋

Theorems

Properties of Floor Functions

Suitable Grade Level

Grades 10-12