From Johannes Widmann's book on "handy and pretty arithmetic for all merchants" The − may be derived from a tilde written over ⟨m⟩ when used to indicate subtraction or it may come from a shorthand version of the letter ⟨m⟩ itself. The + sign is a simplification of the Latin: et (comparable to the evolution of the ampersand &). The symbols (P with overline, p̄, for più (more), i.e., plus, and M with overline, m̄, for meno (less), i.e., minus) appeared for the first time in Luca Pacioli's mathematics compendium, Summa de arithmetica, geometria, proportioni et proportionalità, first printed and published in Venice in 1494. In early 15th century Europe, the letters "P" and "M" were generally used. Nicole Oresme's manuscripts from the 14th century show what may be one of the earliest uses of + as a sign for plus. The Egyptian hieroglyphic sign for addition, for example, resembled a pair of legs walking in the direction in which the text was written ( Egyptian could be written either from right to left or left to right), with the reverse sign indicating subtraction: Though the signs now seem as familiar as the alphabet or the Hindu-Arabic numerals, they are not of great antiquity. Plus and minus are Latin terms meaning "more" and "less", respectively. Their use has been extended to many other meanings, more or less analogous. In addition, + represents the operation of addition, which results in a sum, while − represents subtraction, resulting in a difference. You need to ignore the plus sign and recognize that the second negative means you are subtracting that number.The plus sign + and the minus sign − are mathematical symbols used to represent the notions of positive and negative, respectively. This reads “negative three plus negative 2”. When you are adding a negative number to a negative number, it becomes subtraction, where you start from a negative point on the numbers line and move left.įor example, -3 + (-2). Rule 4: Adding negative numbers to negative numbers- treat the problem like subtraction (counting backwards). How does that look on the numbers line?Īnd then you add the negative number, which means you are moving to the left – in the negative direction. When you are adding a negative number to a positive number you are effectively subtracting the second number from the first.įor example, take 4 + (-2). Rule 3: Adding negative numbers to positive numbers-count backwards, as if you were subtracting. You’re starting with the negative number -6.Īnd you’re adding three to that number, which means you are moving three spots to the right.Ĭlass="green-text">The answer is -3. The best way to think about this problem is to use a number line that extends to the negative numbers. This would reading “negative six plus three”. Pay close attention to where the negative signs are placed in the problem.įor example: -6 + 3. Rule 2: Adding positive numbers to negative numbers-count forward the amount you’re adding. You can calculate these problems the way you always have: 3 + 2 = 5. Rule 1: Adding positive numbers to positive numbers-it’s just normal addition.įor example: this is what you have learned all along. However, there are some simple rules to follow and we introduce them here. When we add a negative number to a positive number, or two negative numbers, that can sometimes seem tricky. Adding positive numbers, such as 2 + 2, is easy.
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