Page 82 - MarceAlgebra Demystified

CHAPTER 4 Negative Numbers 69

2: 70 19 ¼ 89

3: 35 5 ¼ 40

4: 100 8 ¼ 108

5: 99 1 ¼ 100

Double Negatives

A negative sign in front of a quantity can be interpreted to mean ‘‘opposite.’’
For instance 3 can be called ‘‘the opposite of 3.’’ Viewed in this way, we
can see that ð 4Þ means ‘‘the opposite of 4.’’ But the opposite of 4is4:
ð 4Þ¼ 4.

Examples

ð 25Þ¼ 25 ð xÞ¼ x ð 3yÞ¼ 3y

Rewriting a Subtraction Problem as an

Addition Problem

Sometimes in algebra it is easier to think of a subtraction problem as an
addition problem. One advantage to this is that you can rearrange the terms
in an addition problem but not a subtraction problem: 3 þ 4 ¼ 4 þ 3 but
4 3 6¼ 3 4. The minus sign can be replaced with a plus sign if you change
the sign of the number following it: 4 3 ¼ 4 þð 3Þ. The parentheses are
used to show that the sign in front of the 3 is a negative sign and not a minus
sign.

Examples

82 14 ¼ 82 þð 14Þ 20 ð 6Þ¼ 20 þ 6 x y ¼ x þð yÞ