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§ 9.2

§ 9.2. Subtracting Signed Numbers. The opposite of 4 is – 4. – 5. – 4. – 3. – 2. – 1. 0. 1. 2. 3. 4. 5. The sum of a number and its opposite is zero. 10 – 4 = 6. 10 + ( –4) = 6. Subtracting is the same as adding the opposite. 15 – 8 = 7. 15 + ( –8) = 7. 12 – 2 = 10.

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§ 9.2

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1. § 9.2 Subtracting Signed Numbers

2. The opposite of 4 is – 4. – 5 – 4 – 3 – 2 – 1 0 1 2 3 4 5 The sum of a number and its opposite is zero. 10 – 4 = 6 10 + (–4) = 6 Subtracting is the same as adding the opposite. 15 – 8 = 7 15 + (–8) = 7 12 – 2 = 10 12 + (–2) = 10 Opposite Numbers The opposite of a positive number is a negative number with the same absolute value. 4 + (– 4) = 0

3. The opposite of 14 is –14. Change the subtraction to addition. Perform the addition of the two negative numbers. Subtraction of Signed Numbers Subtraction of Signed Numbers To subtract signed numbers, add the opposite of the second number to the first number. Example: Subtract. –6 – 14 –6 + (–14) –20

4. The opposite of –13 is 13. Perform the addition. Change the subtraction to addition. Subtraction of Signed Numbers Example: Subtract. –21 – (–13) –21 + (13) –8 Remember when subtracting two signed numbers: • The first number does not change. • The subtraction sign is changed to addition. • Write the opposite of the second number. • Find the result of the addition problem.

5. Subtraction of Signed Numbers Example: Subtract. Subtraction changed to addition. The LCD is 55. Multiply the fractions. Add the fractions.

6. 5628 feet Difference in altitude 5628 feet – (–350 feet ) Sea level 350 feet Applied Problems with Signed Numbers Example: Find the difference in altitude between a mountain 5628 feet high and a gorge 350 feet below sea level. = 5978 feet 5628 – (–350) = 5628 + 350 = 5978

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