Math Problem Statement

Write the following statement using logical symbols. Let x be a positive integer. Then x = 2, or x is even and x > 2, or x is odd and prime, or x is odd and composite.

Solution

The statement can be written in logical symbols as follows:

Let xx be a positive integer.

x=2  (x is evenx>2)  (x is oddx is prime)  (x is oddx is composite)x = 2 \ \lor \ \left( x \text{ is even} \land x > 2 \right) \ \lor \ \left( x \text{ is odd} \land x \text{ is prime} \right) \ \lor \ \left( x \text{ is odd} \land x \text{ is composite} \right)

Breaking down each condition:

  • x=2x = 2
  • (x is evenx>2)\left( x \text{ is even} \land x > 2 \right) can be expressed as (xmod2=0x>2)\left( x \mod 2 = 0 \land x > 2 \right)
  • (x is oddx is prime)\left( x \text{ is odd} \land x \text{ is prime} \right) can be expressed as (xmod20Prime(x))\left( x \mod 2 \neq 0 \land \text{Prime}(x) \right)
  • (x is oddx is composite)\left( x \text{ is odd} \land x \text{ is composite} \right) can be expressed as (xmod20¬Prime(x)x>1)\left( x \mod 2 \neq 0 \land \neg \text{Prime}(x) \land x > 1 \right)

Thus, the full logical expression is:

x=2  (xmod2=0x>2)  (xmod20Prime(x))  (xmod20¬Prime(x)x>1)x = 2 \ \lor \ \left( x \mod 2 = 0 \land x > 2 \right) \ \lor \ \left( x \mod 2 \neq 0 \land \text{Prime}(x) \right) \ \lor \ \left( x \mod 2 \neq 0 \land \neg \text{Prime}(x) \land x > 1 \right)

Would you like any further details or clarification?


Here are 5 related questions you might explore:

  1. What is the logical symbol for "if and only if" and how does it apply to this statement?
  2. How would you express the condition for xx being a prime number using logical symbols?
  3. Can a number be both even and odd? How would that be expressed in logic?
  4. How does modular arithmetic help in determining whether a number is even or odd?
  5. What are the logical conditions for a number being composite?

Tip: Using modular arithmetic (like xmod2=0x \mod 2 = 0) is a simple way to check if a number is even or odd in logic.

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Math Problem Analysis

Mathematical Concepts

Logic
Modular Arithmetic
Prime and Composite Numbers

Formulas

x = 2
x mod 2 = 0 (x is even)
x mod 2 != 0 (x is odd)
Prime(x) (x is prime)
¬Prime(x) ∧ x > 1 (x is composite)

Theorems

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Suitable Grade Level

Grades 10-12