Adding Real Numbers

MATH 018

Combined Algebra

S. Rook

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Overview

• Section 1.4 in the textbook– Adding Real Numbers– Finding the Opposite of a Real Number

Adding Real Numbers

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How to Add Real Numbers

• Given two real numbers a and b– If a and b have the same sign

• Both are positive or both are negative• Add the positive real numbers (i.e. disregard the signs)• Keep the sign• What is -5 + -7?

– If a and b have different signs• One is positive and one is negative• Subtract the smallest positive real number from the largest

positive real number (i.e. subtract so the result is positive)• Keep the sign of the larger real number• What is 9 + -11?

Adding Real Numbers (Example)

Ex 1: Add (Note that there are NO calculators on Quiz #1!!!):

a) -11.25 + 24.3

b) 5/2 + 9/4 (keep as a fraction)

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Finding the Opposite of a Real Number

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Opposites

• Opposite (of a real number) – the real number that lies the same distance from 0 on the other side of the number line

-(-7) = 7 is read “the opposite of -7 is 7”– Switch the signs

• What is the opposite of a positive number?• What is the opposite of a negative number? • What is the opposite of 0?

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Summary

• After studying these slides, you should know how to do the following:– Add real numbers– Find the opposite of real numbers

• Additional Practice– See the list of suggested problems for 1.4

• Next lesson– Subtracting Real Numbers (Section 1.5)