Answer to Question #319664 in Discrete Mathematics for Jude

Question

Evaluate the truth value of the following propositions using the set (1 ,3, 5, 7)

as the domain.

1. Vx: x (x2 – 4) = 0

2. Ǝx : x + 1 > 0

3. Ǝx : x (x2

– 4) = 0

Answer 1

1. x=0 or (x²-4)=0

$x \not= 0$

So it is false

2.x+1>0

1+1=2>0

So, it is true

3. x(x²-4)=0

$x=0$

$x^2-4=0$

$x= \plusmn 2$

In our set it is no 0,2,-2.

So it is false