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Learn how to subtract integers by adding their opposites, whether positive or negative, through examples and evaluations to enhance mathematical skills.
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Subtracting Integers Sec 2.3 pg. 95 - 97
Subtracting Integers • Let’s look at the following problem. • 5 – 8 • When you subtract 8, it is the same as adding its opposite, - 8. • So, 5 – 8 is the same as 5 + (-8). • |5| = 5 and |- 8| = 8. • Since the signs are not the same, you find the difference between the absolute value. • 8 – 5 = 3. • Is the answer positive or negative? • Negative. The absolute value of – 8 is larger so we use its sign. • 5 – 8 = - 3
Subtracting Integers • To subtract an integer, you add its opposite. • Subtract positive integers. • 5 – 9 • This becomes 5 + (- 9) • |5| = 5 and |-9| = 9. • Find the difference. 9 – 5 = 4 • The absolute value of – 9 was larger, so we take its sign. • 5 – 9 = - 4.
Subtracting Integers • Subtract negative integers. • 10 – (-4) • This become 10 + 4. You add the opposite of a – 4. • 10 + 4 = 14 • -9 – (- 2) • - 9 + 2. • The |-9| = 9 and |2| = 2, so 9 – 2 = 7. This becomes -7 since the absolute value of -9 is larger and we take its sign. • - 9 – ( - 2) = - 7
Evaluate expressions • Evaluate the expression if a = -5 and b = 9 • b – a • This becomes 9 – ( - 5) • To subtract integers you add the opposite, so • 9 + 5 • 14
