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JEE Main 202124 FebruaryEvening Shift
Exam
JEE Main
Year
2021
Date
24 February
Shift
Evening Shift
Subject
Mathematics
Chapter
Mathematical Reasoning

JEE Main 2021 · 24 February · Evening Shift · Mathematics · Mathematical Reasoning

For the statements p and q, consider the following compound...

For the statements pandq,p and q, consider the following compound statements:

\left(a\right)\left(~ q ∧ \left(p \to q\right)\right) \to ~ p</p><p>(b)((p∨q)∧ p)→q</p><p>\left(b\right)\left(\left(p ∨ q\right) ∧ ~ p\right) \to q

Then which of the following statements is correct?

Options

  1. A\left(b\right)isatautologybutnot(a)is a tautology but not \left(a\right).
  2. B(a)\left(a\right) and (b)\left(b\right) both are tautologies.
  3. C(a)\left(a\right) and (b)\left(b\right) both are not tautologies.
  4. D\left(a\right)isatautologybutnot(b)is a tautology but not \left(b\right).

Correct answer

B. (a)\left(a\right) and (b)\left(b\right) both are tautologies.

Step-by-step solution

pp qq  q~ q p→qp \to q  p~ p \left(~ q ∧ \left(p \to q\right)\right)
TT TT FF TT FF FF TT
TT FF TT FF FF FF TT
FF TT FF TT TT FF TT
FF FF TT TT TT TT TT

</p><tableborder="1"cellpadding="1"cellspacing="1"style="width:500px;"><tbody><tr><td></p><table border="1" cellpadding="1" cellspacing="1" style="width: 500px;"> <tbody> <tr> <td>p</td><td></td> <td>q</td><td></td> <td>p ∨ q</td><td></td> <td>~ p</td><td>(p∨q)</td> <td>\left(p ∨ q\right) ∧ ~ p</td></tr><tr><td></td> </tr> <tr> <td>T</td><td></td> <td>T</td><td></td> <td>T</td><td></td> <td>F</td><td></td> <td>F</td><td></td> <td>T</td></tr><tr><td></td> </tr> <tr> <td>T</td><td></td> <td>F</td><td></td> <td>T</td><td></td> <td>F</td><td></td> <td>F</td><td></td> <td>T</td></tr><tr><td></td> </tr> <tr> <td>F</td><td></td> <td>T</td><td></td> <td>T</td><td></td> <td>T</td><td></td> <td>T</td><td></td> <td>T</td></tr><tr><td></td> </tr> <tr> <td>F</td><td></td> <td>F</td><td></td> <td>F</td><td></td> <td>T</td><td></td> <td>F</td><td></td> <td>T

Both are tautologies

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