check these:
http://www.targetiit.com/iit-jee-forum/posts/for-guys-who-just-gave-xth-exams-18905.html
http://www.targetiit.com/iit-jee-forum/posts/positive-or-negative-17411.html
Is zero both +ve & -ve?
Why can't any number be divided by 0?
check these:
http://www.targetiit.com/iit-jee-forum/posts/for-guys-who-just-gave-xth-exams-18905.html
http://www.targetiit.com/iit-jee-forum/posts/positive-or-negative-17411.html