Rules for Addition and Multiplication of Integers

1. All numbers have signs - either Positive or Negative.
• If you do not see them they are understood to be there. e.g.:
  • 4 = +4 (if a positive number is alone, its sign can be omitted and understood to be there.)
  • 5p -7 means +5p + -7( if a positive number is first in an expression, its sign can be omitted and understood to be there.)
2. The Addition and Multiplication signs are often omitted and are understood to be present.
• 6+4 means +6 + +4
• 7-2 means +7 + -2
• 7b means 7.b
• (-2)(-4) means -2 . -4
3. The sign which appears belongs to the number that follows it.
• 4a -7 + 5a -3a means 4.a + -7 + +5.a + -3.a
4. There is no subtraction - instead, add a negative number.
   • 8-6 means 8 + -6

5. Rules
   To Add two numbers that have the same sign: Add the numbers, give the answer the same sign	1) -6-9 = -6 + -9 = -15 2) 7+8 = +7 + +8 = +15 = 15
   To Add two numbers that have different signs: Subtract the numbers, give the answer the sign of the bigger number.	1) -6+9 = -6 + +9 = +3 = 3 2) 7+-8 = +7 + -8 = -1
   When you Multiply (or Divide) two numbers that have : the same sign, the answer is Positive 4.3 = +4 . +3 = +12 = 12 -5.-6 = +30 = 30 different signs, the answer is Negative -7.4 = -7.+4 = -28 5.-3 = +5.-3 = -15	When you Multiply (or Divide) two numbers that have : the same sign, the answer is Positive 14/2 = +14 / +2 = +7 = 7 -15 / -3 = +5 = 5 different signs, the answer is Negative -27/9 = -27 / +9 = -3 25/-5 = +25 / -5 = -5