Propositional Logic · First-Order Logic (Optional)

Lesson 9

Nikolai Chukhin · Alexander S. Kulikov

Problem. Which of the following formulas is satisfied by the model \(L\)?

1 point

  1. \(\forall x \ \exists y (x = y + y)\)

  2. \(\forall x (x \times 0 = 0)\)

  3. \(\forall x \ \forall y \ (x \times y = y \times x)\)

  4. \(\forall x \ \exists y \ (x \times y = x)\)

  5. \(\forall x \ (x \neq x + 1)\)

  6. \(\forall x , \forall y \ \forall z \ (x + z = y + z \Rightarrow x = y)\)