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If we have 3 pizzas and we go and get 2 more
pizzas we have 5 pizzas: |
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3 Pizzas + 2
Pizzas = 5 Pizzas
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Letters in math work the same way as pizzas. |
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If we
have 3X and we go and get 2X more, we have 5X: |
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3 X + 2 X = 5
X
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Just think of the letter X like the word pizza. |
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5
was the number of pizzas we had. |
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5 is the number of X's we
have. |
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We can do subtraction like this
too: |
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6 X - 2 X = 4
X
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(Just like 6
pizzas - 2 pizzas = 4 pizzas)
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If somebody asked us you to add the number 6 and 3
pizzas, |
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you really couldn't do it. Numbers and pizzas don't mix. |
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The same
goes for trying to add stuff like: |
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3 X +
2
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We have 3 X's plus a silly 2. |
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You can't add them
together. |
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So 3X + 2 is just 3X + 2 |
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If we tried to add 3 pizzas and 4 bowling balls,
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all we
would get is a big mess. |
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You really can't add different stuff like
this together |
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and get anything that makes sense. |
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The same thing goes for
different letters. |
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An X and a Y are as different as bowling balls and
pizzas. |
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You just CAN'T add them together. |
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So ... |
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3 X + 4 Y
is just 3 X + 4 Y
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Let's go back to stuff we can
combine. |
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What could
we do with something like this: |
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3 X + 4 Y + 2 X
- 6 + 7 + 3Y
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We have 2
different X things in that mess. |
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We can
combine the two of them: |
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3 X + 2 X = 5
X
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Along with the rest of the glob we now
have: |
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5 X + 4 Y - 6 +
7 + 3Y
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We can combine the Y's. 4Y + 3Y = 7Y. |
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So we now
have: |
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5 X + 7 Y - 6 +
7
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We can also combine the -6 and the
+7 |
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-6 + 7 = 1 (Start at - 6 and go up 7). |
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That means
we now have. |
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5 X + 7 Y +
1
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Now, all the things that had the same letter (or
no letter) |
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have been combined. |
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That
means we're done. |
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When two or more things have the same letter (or
no letter) |
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we call them: |
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LIKE
TERMS
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A
Term
means any number, letter, or group of numbers and letters |
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that are
separated from other things by a + or a -. |
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Like
means any term that has the same letter or letters. |
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The same exponent on
the letter or letters. Or no letters at all. |
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copyright 2005 Bruce Kirkpatrick |
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