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Mr. Borosky Section 2.2 2.2 Add Real Numbers p. 74-79 Algebra 1 Objective: 1. You will add positive and negative numbers. One way to add real numbers is to use the number line Key Concept Box p. 75 Rules of Addition Words To add 2 numbers with the same sign add their absolute values. The sum has the same sign as the numbers added. To add 2 numbers with different signs subtract the lesser absolute value from the greater absolute value. The sum has the same sign as the number with the greater absolute value. Property Commutative Examples 8 + 7 = 15 -6 + (-10) = -16 -12 + 7 = -5 18 + (-4) = 14 Properties of Addition Algebra Words a + b = b + a The order in which you add 3 + (-2) = -2 + 3 2 numbers does not change the sum Associative (a + b) + c = a + (b + c) (-3 + 2) + 1 = -3 + (2+1) The way you group 3 numbers in a sum does not change the sum Identity a + 0 = a or 0 + a = a -5 + 0 = -5 0 + 8 = 8 The sum of a number and 0 is the number Inverse a + (-a) = 0 or –a + a =0 3 + (-3) = 0 -6 + 6 = 0 The sum of a number and its opposite is 0 Additive Identity – the number 0 since anything plus 0 is itself. Additive Inverse (Opposite) - numbers that are the same distance from the origin but on opposite sides of the origin. It is the opposite of a. Ex. The opposite of -3 is 3, The opposite of 5 is -5, the opposite of 0 is 0 2.2 Add Real Numbers p. 74-79 Page 1 of 1