Considering some key concepts that are the corner stone of your math skills and that are fundamental to achieve the better score on the GRE test, let's start reviewing sets of numbers and their properties. On the GRE the word numbers actually means real numbers, which can be conceptualized and represented on the number line above.

The numbers to the right of zero are called positive numbers and those to the left are called negative. The first ones must be written with the positive (+) sign in front and the second ones with the negative sign in front (-).These numbers are also identified as signed numbers.

Important facts are also being true and are worth to remember as cold.

1) for any number a, one and only one of the following statements are true

• a is negative
• a is = to zero
• a is positive

Right away is important to denote that the absolute value of a number a, | a |, is the distance between a and zero on the number line, both on the positive side and negative one. The number a, for instance 5, is 5 units apart from zero and -5 is 5 units apart from zero on the negative side. As such, their absolute value is |5|. In this scenario 5 and - 5 are opposite numbers. The only number that is equal to its opposite is zero

2) The product of any number * zero is zero. And if the product of two numbers is zero, then at least one of the two is zero.

We need to consider that our numbers on the number line, and we are talking not only of integers but also NOT integers, can be the product or quotient of two positive numbers or two negative ones; or a mix: one positive or one negative.

3) The product and quotient of two positive numbers or two negative numbers are positive; the product and quotiet of a positive number and a negative number are negative.