ARITHMETIC : Integers, fractions..
 Integers : ..3,2,1,0,1,2,...
 0 is neither neither positive or negative. 0 is even number.
 real numbers are integers and have decimal values between them..
 a^{0}=1, 1/a^{n}=a^{n}
 The absolute value of a number N, denoted by N , is defined to be N if N
is positive or zero and N if N is negative. Example 5 =5
 Integer divisible by 2 is called even integer (including 0 and 2). Examples are 8,6,4,2,0,2,4,6,8
 Factors of a number are it's divisors. For instance, the factors of 21 are 3 and 7, because 3*7 = 21.
 The greatest common divisor (or greatest common factor) of two nonzero integers x and y is the
greatest positive integer that is a divisor of both x and y. For example GCF of 30 and 45 is 15, GCF of 60 and 90 is 30.
 A prime number is an integer greater than 1 that has only two positive divisors: 1 and itself, examples are 2,3,5,7,11,13,17 (remember 2 is a prime number)
 Fractions are numbers in the form (x/y) where y is never 0. Examples: 3/5, 7/8
 Exponents and roots. (you will always find few questions on this)
