Write down the negation of following compound statements. (i) All rational numbers are real and complex.
Write down the negation of following compound statements.
(i) All rational numbers are real and complex.
(ii) All real numbers are rationals or irrationals.
(iii) x = 2 and x = 3 are roots of the quadratic equation x2 -5x +6 = 0
(iv) A triangle has either 3-sides or 4-sides.
(v) 35 is a prime number or a composite number.
(vi) All prime integers are either even or odd.
(vii) |x| is equal to either x or -x.
(viii) 6 is divisible by 2 and 3.
1 Answers
(i) Let p: All rational numbers are real.
q: All rational numbers are complex.
~ p: All rational numbers are not real.
~ q ; All rational numbers are not complex.
Then, the negation of the given compound statement is:
~ (p ∧ q): All rational numbers are not real or not complex.
[~(p ∧ q) = ~p v ~q]
(ii) Let p: All real numbers are rationals. q: All real numbers are irrationals. Then, the negation of the given compound statement is:
~ (p v q): All real numbers are not rational and all real numbers are not irrational. [~(p v q) = ~p ∧ ~ q]
(iii) Let p ; x = 2 is root of quadratic equation x2 – 5x + 6 = 0. q: x = 3 is root of quadratic equation x2 – 5x + 6 = 0.
Then, the negation of the given compound statement is:
~ (p ∧ q) : x = 2 is not a root of quadratic equation x2 – 5x + 6 = 0 or x = 3 is not a root of the quadratic equation x2 – 5x + 6 = 0.
(iv) Let p: A triangle has 3-sides. q: A triangle has 4-sides.
Then, the negation of the given compound statement is:
~ (p v q): A triangle has neither 3-sides nor 4-sides.
(v) Let p: 35 is a prime number. q: 35 is a composite number.
Then, the negation of the given compound statement is:
~ (p v q): 35 is not a prime number and it is not a composite number.
(vi) Let p: All prime integers are even. q: All prime integers are odd.
Then, the negation of the given compound statement is given by
~(p v q): All prime integers are not even and all prime integers are not odd.
(vii) Let p:|x| is equal to x. q: |x| is equal to —x.
Then, the negation of the given compound statement is:
~ (p v q): |x| is not equal to JC and it is not equal to —x.
(viii) Let p: 6 is divisible by 2.
q: 6 is divisible by 3.
Then, the negation of the given compound statement is:
~ (p∧q): 6 is not divisible by 2 or it is not divisible by 3