Adding two positive integers results in a positive number, and adding two negative integers yields a negative number. Multiplying two negative or two positive integers makes a positive number, but multiplying a negative by a positive yields a negative integer. Similarly, dividing a positive by a positive or a negative by a negative gives a positive answer, but dividing a positive by a negative or a negative by a positive always results in a negative solution.
Continue ReadingExamples of the rules above for adding integers are 3 + 4 = 7 and -3 + -4 = -7. When adding positive and negative numbers together, the sign of the integer with the greatest absolute value is the sign of the solution. For instance, -4 + 3 = -1. The negative four has the highest absolute value, four, so the answer is negative. In the problem -3 + 4 = 1, the positive four has the highest absolute value, so the answer is positive.
Multiplication examples are 3 x 4 = 12, -3 x -4 = 12, -3 x 4 = -12 and 3 x -4 = -12. Examples of the division rules above are 15/3 = 5, 15/-3 =-5, -15/-3 =5 and -15/3 = -5.
Subtraction is a little trickier. Subtracting a positive integer from a negative integer yields a negative, as in -5 - 4 = -9. Subtracting a negative number from a positive always yields a positive, as in 5 - (-4) = 9. Subtracting a negative integer is the equivalent of adding a positive integer.
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