# Thread: How to write propositions into symbolic forms

1. ## How to write propositions into symbolic forms

Well I was wondering if there is a method which some one follows to solve questions like these..

Here is an example

The square of every real number is a non-negative number

(for all x)(x element of Z) --> (x^2>0)

is this how you write it ? btw I used A upside down for (for all x)

if you can kindly post any websites that teaches how to master this

Thanks

2. http://en.wikipedia.org/wiki/Set_(mathematics)

this is what I founded in 1 min., just google it... and you will find what you want.

3. ## Introduction to Logic

Hello Khonics89
Originally Posted by Khonics89
Well I was wondering if there is a method which some one follows to solve questions like these..

Here is an example

The square of every real number is a non-negative number

(for all x)(x element of Z) --> (x^2>0)

is this how you write it ? btw I used A upside down for (for all x)

if you can kindly post any websites that teaches how to master this

Thanks
You have nearly got it right. We usually use $\mathbb{R}$ to denote the real numbers, and 'non-negative' means 'greater than or equal to zero'. So the correct answer would be:

$\forall x [(x\in\mathbb{R}) \Rightarrow (x^2 \ge 0)]$

If you want some on-line material that introduces Logic to a beginner, you'll find some notes (with lots of worked examples and exercises) that I wrote for Wikibooks starting just here. And in particular, the use of quantifiers is covered just here.