Math Problem Statement

Which of the following is the negation of the statement 'Square of a negative real number is positive'?

Solution

The given statement is:

"Square of a negative real number is positive."

We need to negate this statement, and we have the following options.

Let's break down the original statement:

  1. Original statement in logical terms: "For all xx, if xx is less than 0, then x2>0x^2 > 0" (since the square of any real number is positive).
    • In symbolic form: x((x<0)(x2>0))\forall x ((x < 0) \to (x^2 > 0)).

Negation of the statement:

The negation of the statement "For all xx, if x<0x < 0, then x2>0x^2 > 0" would be "There exists some xx such that x<0x < 0 and x20x^2 \leq 0" (i.e., the square of some negative number is non-positive, meaning it is 0 or negative).

This leads us to the option that matches the negation:

  • Option C: x((x<0)(x20))\exists x ((x < 0) \land (x^2 \leq 0))

This correctly represents the negation of the original statement. Therefore, the correct answer is:

C) x((x<0)(x20))\exists x ((x < 0) \land (x^2 \leq 0)).


Would you like more details on the logical steps involved? Here are five related questions you can explore:

  1. What are the rules for negating "for all" (\forall) and "there exists" (\exists) quantifiers?
  2. How do implications (\to) work in logical statements?
  3. Why does the square of a real number always result in a non-negative number?
  4. What are the properties of real numbers under squaring?
  5. How do logical conjunction (\land) and disjunction (\lor) work in truth tables?

Tip: When negating a statement involving "for all" (\forall), it turns into "there exists" (\exists), and the internal logical condition flips accordingly.

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Math Problem Analysis

Mathematical Concepts

Logic
Negation
Quantifiers
Real Numbers
Algebra

Formulas

-

Theorems

Negation of logical quantifiers

Suitable Grade Level

Undergraduate or Advanced High School