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Sign Operations
07/27/12 lntaylor ©
Table of Contents
Learning Objectives
Signs and symbols mean different things
Memorizing Opposite symbols
Practice
07/27/12 lntaylor ©
LO1:
LO2:
Define and differentiate signs and symbols
Eliminate 80% of your mistakes by focusing on signs and symbols
07/27/12 lntaylor ©TOC
Learning Objectives
Def1:
Def2:
Sign – there are only two signs + and -
Symbols in math tell you what to do (operations)
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Definitions
PK1: Knowledge of mathematical symbols
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Previous Knowledge
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Signs Meaning
+ Positive number to the right of 0
- Negative number to the left of 0
Note1:
Note 2:
There are only 2 signs
They are seldom used properlyIt is true!!
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Symbols Operations Meaning
+ Do not change the following sign(s)Also means go right
- Change the following sign(s)Also means go left
x,*,( ) Multiply numbers next to symbol
/, − Divide numbers next to symbol
Root of the number under the symbol
= Left side is exactly the same as the right side
< Left side is less than right side
> Left side is greater than right side
< Left side is less than or the same as right side
> Left side is greater or the same as right side
Note 1:
Note 2:
There are lots of symbols
They are seldom used properlyIt is true!!
Signs and Symbols
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Step1:
Step2:
Sign – there are only two signs + and -
There are no signs in this problemThere are only symbols telling you what to do
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3 + 1 = 4
These are symbols
Step3: Where are the signs?Let me show youThe signs are in red and the symbols in gold
+ 3 + + 1 = + 4
Step4: The first + is a symbol telling you not to change the second +Let me show you
Do not change the positive number!
Note: The + means start at 3 and go to the right 1Hard to believe? Let me show you more.
3 + 1 = 4
Step1:
Step2:
Sign – there are only two signs + and -
There are no signs in this problemThere are only symbols telling you what to do
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3 - 1 = 2
These are symbols
Step3: Where are the signs?Let me show youThe signs are in red and the symbols in gold
+ 3 - + 1 = + 2
Step4: The first - is a symbol telling you to change the second +Let me show you
Change the positive number!
Note:
3 - 1 = 2
The - means start at 3 and go to the left 1Hard to believe? Let me show you more.
Step1:
Step2:
Sign – there are only two signs + and -
There is an extra sign in this problemAnd a symbol telling you what to do
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3 - - 1 = 4
This is a symbol
Step3: Where are the signs?Let me show youThe signs are in red and the symbols in gold
+ 3 - - 1 = + 4
Step4: The - is a symbol telling you to change the -Let me show you
Change the negative number!
Note: See/ there are no positive and negative signs…only symbolic operations
3 + 1 = 4
This is a sign
Step1:
Step2:
Sign – there are only two signs + and -
There are no signs in this problemThere are only symbols telling you what to do
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-3(4) + 2 = -10
These are symbols
Step3: The first – says start at 0, go left 3 times (4 units each time or 12 units)The next symbol + says go to the right 2 from where you wereThe last symbol says you will end up 10 left of 0
- 12 + 2 = - 10
Note: Do you see that symbols tell you what to doand signs tell you where you are?
-12 -10 0
Step1:
Step2:
Sign – there are only two signs + and -
There are no signs in this problemThere are only symbols telling you what to do
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-3(4x + 5) + 2 = -12x - 13
Step3: The first symbol – says start at 0, go left 3 times (4x + 5 each time)This is why - ( )means change the signs in the ( ) after you multiplyThe next symbol + says do not change the sign
- 3( + 4x + 5) + 2 = - 12x - 13
Note: Do you see that symbols tell you what to doand signs tell you where you are?
– 12x – 15 + 2 = – 12x – 13
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Note1:
Note2:
Now you know the difference between signs and symbols
What you thought was a signis really a symbol telling you go left or right
-12 - 4 0 6 10 12
-12 + 18 – 10 + 14 = 10
Start at 0Go left 12Go right 18Go left 10Go right 14You will end up at 10 to the right of 0
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Memorizing opposite symbols
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Symbol What is its opposite?
+
-
*
/
xe
> -
>
>
>
>
>
+
/
*
xe
√ xclear answers
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Practice
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Sign Problem Answer
3(4x – 5) = ?
9 - -12 = ?
-4(-5 + 3x) = ?
-3(3x – 3) – 2(3x + 6) = ?
-4(-5 -6x) = ?
-4(4x2 + 5) = ?
> 12x - 15
>
>
>
>
>
21
20 – 12x
- 15x - 3
20 + 24x
- 16x2 - 20
clear answers
