Mathematical Logic and Quantifiers Quiz

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Questions and Answers

Which of the following is the correct symbol for 'for all'?

  • (correct)

The statement '∃ x, x is a prime number' is true.

True (A)

What does the symbol '⇒' represent in mathematical logic?

Implication

The statement 'If it is raining, then the ground is wet' can be written in symbolic form as P ______ Q.

<p>⇒</p> Signup and view all the answers

Match the following symbols with their corresponding meanings:

<p>∃ = There exists ∀ = For all ⇒ = Implies ⇐ = Is implied by</p> Signup and view all the answers

Which of the following statements is true regarding the Euler Diagram representing P ⇒ Q?

<p>If you are in the P ellipse, you must also be in the Q ellipse. (C)</p> Signup and view all the answers

The statement '∀ x, x² ≥ 0' means that all real numbers have negative squares.

<p>False (B)</p> Signup and view all the answers

What is the most relevant quantifier to add to the statement 'm is an even number' to make it true as often as possible?

<p>∃</p> Signup and view all the answers

What can be concluded about the product of any three consecutive numbers?

<p>It is always even. (A)</p> Signup and view all the answers

The sum of any four consecutive numbers is odd.

<p>False (B)</p> Signup and view all the answers

What is the remainder when $a^k$ is divided by 5 if $a$ is not divisible by 5?

<p>1 or 4</p> Signup and view all the answers

The expression $(k^3 - k)(2k^2 + 5k - 3)$ is divisible by _____ without using induction.

<p>5</p> Signup and view all the answers

Match the following statements with their proofs:

<p>The product of three consecutive numbers is even = At least one number will be even $n^2 - 1$ is divisible by 3 for $n$ not a multiple of 3 = The possible forms of $n$ are explored The sum of four consecutive numbers is even = They can be expressed as a group of two pairs of even numbers</p> Signup and view all the answers

What happens to the inequality sign when multiplying both sides by a positive number?

<p>It stays the same (B)</p> Signup and view all the answers

Dividing both sides of an inequality by a negative number will keep the sign the same.

<p>False (B)</p> Signup and view all the answers

What should you do when performing an operation that matches a function that is not monotonic?

<p>Get more information</p> Signup and view all the answers

When taking the tangent of both sides of an inequality, we need _______ to determine the behavior.

<p>more information</p> Signup and view all the answers

Match the operation with its effect on the inequality sign:

<p>Multiplying by 3 = Stays the same Dividing by -2 = Swaps Taking the negative reciprocal = More information needed Taking the square root = Stays the same under certain conditions</p> Signup and view all the answers

For which operation will the sign definitely change?

<p>Multiplying by -1 (A)</p> Signup and view all the answers

Taking the reciprocal of both sides of an inequality never requires more information.

<p>False (B)</p> Signup and view all the answers

If a > b > 0, what can we conclude about 2^{-a} compared to 2^{-b}?

<p>2^{-a} &lt; 2^{-b}</p> Signup and view all the answers

What is a suitable approach for proving a statement is false?

<p>Direct proof leading to a contradiction (C)</p> Signup and view all the answers

Proof by cases requires each case to support the statement.

<p>False (B)</p> Signup and view all the answers

What is the contradiction when proving that there cannot be a Pythagorean triad where all numbers are odd?

<p>The left-hand side is not a multiple of 4 while the right-hand side is.</p> Signup and view all the answers

The sum of the squares of two consecutive even numbers is divisible by ____ but not by ____.

<p>4, 8</p> Signup and view all the answers

For which of the following statements is a real number solution found?

<p>There exists a real number n such that 3n + 4n = 5n. (D)</p> Signup and view all the answers

There exists a real number x such that x^2 + 2x + 5 < 0.

<p>False (B)</p> Signup and view all the answers

What is the general form to express two consecutive even numbers using an integer k?

<p>2k and 2k + 2</p> Signup and view all the answers

Match the proof techniques with their descriptions:

<p>Direct proof = Proving a statement directly with logical steps Contradiction = Assuming the opposite and finding a contradiction Proof by contrapositive = Proving ¬Q ⇒ P to establish the statement is false Proof by cases = Considering separate cases that lead to contradictions</p> Signup and view all the answers

What is the negation of the statement '𝑥 ≥ 4'?

<p>𝑥 ≤ 4 (A)</p> Signup and view all the answers

The statement 'If 𝑥 is composite, then 2𝑥 + 1 is prime' has the same contrapositive as 'If 2𝑥 + 1 is not prime, then 𝑥 is not composite.'

<p>True (A)</p> Signup and view all the answers

What is the concept of negation in mathematics?

<p>Negation refers to the denial or contradiction of a statement, indicating what is not true.</p> Signup and view all the answers

The negation of the statement '𝑥 < 5' is __________.

<p>𝑥 ≥ 5</p> Signup and view all the answers

Match the inequality with its negation:

<p>𝑥 &gt; 2 = 𝑥 ≤ 2 𝑥 ≤ 3 = 𝑥 &gt; 3 𝑥 = 5 = 𝑥 ≠ 5 𝑥 &lt; 1 = 𝑥 ≥ 1</p> Signup and view all the answers

Which of the following statements is NOT an example of negation?

<p>∃ an integer 𝑥 such that 𝑥 = 0 becomes ∀ integer 𝑥, 𝑥 ≠ 0 (C)</p> Signup and view all the answers

The contrapositive of the statement 'If 𝑥 is even, then 𝑥^2 is even' is 'If 𝑥^2 is not even, then 𝑥 is not even.'

<p>True (A)</p> Signup and view all the answers

What does proof by contradiction entail?

<p>Proof by contradiction involves assuming the opposite of what you want to prove and then showing that this assumption leads to a contradiction.</p> Signup and view all the answers

Which of the following statements about multiples of 3 and multiples of 9 is true?

<p>A number is a multiple of 9 if it is a multiple of 3. (A), A number can be a multiple of 3 without being a multiple of 9. (D)</p> Signup and view all the answers

The sum of any four consecutive integers is always odd.

<p>False (B)</p> Signup and view all the answers

What is the product of any two odd integers?

<p>odd</p> Signup and view all the answers

If m is an even integer, then 𝑚2 is ___.

<p>even</p> Signup and view all the answers

Match the following properties with their corresponding outcomes:

<p>The product of any three consecutive integers = Is even The sum of any four consecutive integers = Is even The sum of two odd integers = Is even The sum of two even integers = Is even</p> Signup and view all the answers

Which of the following correctly states a property regarding multiples of 16?

<p>If m is a multiple of 4, then m² is a multiple of 16. (C)</p> Signup and view all the answers

The product of any two even integers is always odd.

<p>False (B)</p> Signup and view all the answers

What is the result of adding two odd integers?

<p>even</p> Signup and view all the answers

The expression for the sum of two consecutive integers k and (k + 1) is ___.

<p>2k + 1</p> Signup and view all the answers

What can be concluded about the sum of an odd and an even integer?

<p>The sum is odd. (C)</p> Signup and view all the answers

Flashcards

Product of consecutive numbers

The product of any three consecutive integers is even.

Sum of four consecutive numbers

The sum of any four consecutive integers is always even.

Remainder of a^k - b^k

The expression has a remainder of 1 when divided by 3.

Divisibility of n^2 - 1

n^2 - 1 is divisible by 3 if n is not a multiple of 3.

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Remainders of squares mod 5

The remainder when a² is divided by 5 is 1 or 4 if a is not divisible by 5.

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Implication (P ⇒ Q)

If P is true, then Q must also be true.

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Reverse Implication (Q ⇐ P)

If Q is true, then P must also be true.

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Euler Diagram

A visual representation showing the relationship between sets or propositions.

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Quantifiers: For all (∀)

Indicates a statement is true for every instance of a variable.

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Quantifiers: There exists (∃)

Indicates that there is at least one instance where the statement is true.

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Example of P and Q

P: n is a positive integer; Q: n is an even number greater than 0.

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True or False (P ⇒ Q)

P doesn't guarantee Q, but Q guarantees P in some cases.

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Integer Properties

Even numbers are also integers, but not all integers are even.

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Multiples of 3 vs. 9

If a number is a multiple of 9, it is also a multiple of 3, but not the other way around.

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Odd products of odd numbers

The product of two odd integers is always odd.

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Even sum of even numbers

The sum of two odd integers results in an even integer.

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Square of even number

The square of an even number is always even.

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Consecutive integers product

The product of any three consecutive integers is even.

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Sum of consecutive integers

The sum of any four consecutive integers is always even.

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Multiple of 16

If a number is a multiple of 4 and squared, the result is a multiple of 16.

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Cosine ratio bounds

The cosine of an angle ranges between -1 and 1.

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Squares less than or equal to 2

Only integers 0 and ±1 squared are less than or equal to 2.

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Squared even integer

If m is an even integer, then m squared is also even.

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Direct Proof

A method of proving statements by showing them to be true directly.

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Proof by Contradiction

A proof method showing that assuming the opposite leads to a contradiction.

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Positive Definite Quadratic

A quadratic expression that is always positive for all real numbers.

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Pythagorean Triad

A set of three integers a, b, c satisfying a² + b² = c².

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Sum of Squares of Even Numbers

The sum of squares of two consecutive even numbers is divisible by 4 but not 8.

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Existence of Real Numbers

A statement can be true if a specific real number exists that satisfies it.

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Proof of Evenness

To prove x is even, show x² is even and vice versa.

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Contradicting Statement

A statement is shown to be false through contradicting all cases or assumptions.

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Negation

The opposite of a given statement, changing true to false and vice versa.

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Negation of equality

The negation of equality (a = b) is not equal (a ≠ b).

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Negation of inequality

Negating inequalities changes their direction: x > 2 becomes x ≤ 2.

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Existential quantifier negation

Negation of '∃' (there exists) is '∀' (for all), signaling that none meet the criteria.

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Universal quantifier negation

Negation of '∀' (for all) is '∃' (there exists), indicating at least one meets the criteria.

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Contrapositive

The contrapositive of a statement reverses and negates the hypothesis and conclusion.

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Proof by contrapositive

A method of proving a statement by proving its contrapositive instead of the statement itself.

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Euler Diagram in negation

Illustrates negation visually, showing areas of a set and its complement.

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Monotonic Increasing Function

A function where an increase in input results in an equal or greater output.

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Monotonic Decreasing Function

A function where an increase in input results in an equal or smaller output.

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Operations for Inequalities

Add, subtract, multiply or divide by positive keeps sign; negative swaps sign.

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Sign Swap

The inequality sign changes when multiplying or dividing by a negative number.

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Discontinuous Functions

Functions like tangent or reciprocals that can have breaks or jumps.

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Taking Reciprocals

Finding 1/x can lead to discontinuity in inequalities.

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Assumption of Positivity

Assuming values are positive can affect the outcome of functions like square roots.

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Equality

Refers to conditions under which two expressions can be equal.

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Study Notes

HSC Mathematics Extension 2

  • This is a textbook for the 2017 NSW Syllabus
  • Created and maintained by Steve Howard
  • Updates are available at howardmathematics.com
  • The author grants Australian schools a license to use the textbook for non-commercial use.
  • Commercial use is prohibited.
  • Teachers can use example questions for assessment without attribution.

Content Outline

  • Part 1:

    • Chapter 1: Nature of Proof
      • Language of Proof and Simple Proofs
      • Proof by Contrapositive
      • Proof by Contradiction
      • Equivalence and Disproofs
      • Inequality Proofs
      • Arithmetic Mean - Geometric Mean Inequality
    • Chapter 2: Complex Numbers
      • Introduction to Complex Numbers
      • Cartesian Form
      • Mod-arg Form
      • Exponential Form
      • Square Roots
      • Conjugate Theorems
      • Complex Numbers as Vectors
      • Curves and Regions
      • De Moivre's Theorem
      • Complex Roots
      • Appendices: Converting Between Cartesian and Polar Forms on a Calculator
      • Finding e and ei Using the Limit Definition
      • Proving Euler's Formula from the Taylor Series
  • Chapter 4: Integration

  • Chapter 5: Vectors

  • Chapter 6: Mechanics

  • Appendices: Additional information and worked examples for different chapters and topics

Further Information

  • The textbook is intended to match past HSC questions where possible, starting with the basics, then progressing to medium and challenging difficulties.
  • The 1000 revision questions, linked to the corresponding chapters, provide additional practice.
  • The 42 lessons structure aids in timely course completion for effective revision.
  • The author encourages feedback and suggestions for improvements.

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