1.简单
真值表中恰有一行使 (a ∨ b) → a 为假。点选这一行。
(a ∨ b) → a
- 1a = 1, b = 1
- 2a = 1, b = 0
- 3a = 0, b = 1
- 4a = 0, b = 0
2.简单
真值表中恰有一行使 (¬p → q) ∨ p 为假。点选这一行。
(¬p → q) ∨ p
- 1p = 1, q = 1
- 2p = 1, q = 0
- 3p = 0, q = 1
- 4p = 0, q = 0
3.中等
在其真值表的 8 行中,(a ↔ c) ↔ ((b ∧ c) ∧ (b ∧ a)) 在多少行为真?把这个数记作 N。
(a ↔ c) ↔ ((b ∧ c) ∧ (b ∧ a))
N =
4.中等
哪个公式与 ¬(a ↔ b) 在逻辑上等价?点选它。
¬(a ↔ b)
- 1¬a ∨ ¬b
- 2a ↔ ¬b
- 3¬a ↔ ¬b
- 4a ∧ ¬b
5.困难
把否定完全移到内部之后,哪个命题与 ¬∀x (A(x) → B(x)) 等价?点选它。
¬∀x (A(x) → B(x))
- 1∃x (¬A(x) ∧ B(x))
- 2∃x (A(x) ∧ ¬B(x))
- 3∃x (A(x) → ¬B(x))
- 4∀x (A(x) ∧ ¬B(x))
6.困难
前提为 c → b; a → b、结论为 c → a 的论证是无效的。点选真值表中作为反例的那一行。
c → ba → b∴ c → a
- 1a = 1, b = 1, c = 1
- 2a = 1, b = 1, c = 0
- 3a = 1, b = 0, c = 1
- 4a = 1, b = 0, c = 0
- 5a = 0, b = 1, c = 1
- 6a = 0, b = 1, c = 0
- 7a = 0, b = 0, c = 1
- 8a = 0, b = 0, c = 0
答案
- 1. a = 0, b = 1
- 2. p = 0, q = 0
- 3. N = 5
- 4. a ↔ ¬b
- 5. ∃x (A(x) ∧ ¬B(x))
- 6. a = 0, b = 1, c = 1
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