Inopeki
FOILing, do i multiply or add?
Like (2x+4)+(2x+4)
i add there, right? And
(2x+4)*(2x+4)
I multiply there, right?
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anonymous
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yes
Inopeki
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I did that in class todya but i didnt get the right answer..
anonymous
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what did you get for the first one?
Inopeki
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(2x+4)+(2x+4)
4x+2x+4+4+2x+4+4
8x+16
anonymous
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hmm
anonymous
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it looks like you are multiplying and adding instead of adding.
the parentheses here are unnecessary
amistre64
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when it says to add, I would add.
and when it says to multiply, id multiply.
but thats just me set in my ways :)
anonymous
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\[(2x+4)+(2x+4)=2x+4+2x+4=2x+2x+4+4\]
anonymous
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let's imagine for a moment that x was ten (x is a variable, but it could be ten)
then
\[2x+4=2\times 10+4=24\] and
\[24+24=48\]
Inopeki
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I thought it was like this
|dw:1327066387934:dw|
anonymous
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multiplication distributes over addition. so if you had
\[(2x+4)(2x+4)\] you would use the distributive law, just like if you had
\[24\times 24\]
Inopeki
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But wheres the x?
Tomas.A
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addition is commutative you can remove brackets when you have ONLY addition
anonymous
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but addition is the same as "combine like terms" just as you would with arithmetic
24
+ 24
______
48
2x + 4
+ 2x + 4
__________
4x + 8
amistre64
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2x+4
(+) 2x+4
--------
4x+ 8
2x+4
(x) 2x+4
---------
8x+16
4xx+8x
-----------------
4x^2+16x+16
Inopeki
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Why would it be 4x^2+16x+16?
anonymous
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@inopeki i was making an analogy. the work you do with variables is a generalization of the work you do in arithmetic, and if it doesn't work with arithmetic it certainly doesn't work with variables, because the variable could be a number, that is you could replace the variable by a number
amistre64
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becasue thats what happens when you multiply stuff
Inopeki
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Oh ok
Inopeki
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so basically just add them up?
Inopeki
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2x+4
(+) 2x+4
--------
4x+ 8
anonymous
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imagine your job was to add
\[24+24\]\ what would you do? line them up and add
amistre64
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5+3 = 8
(x) 2+4 = 6
------------
20+12
10+6
--------------
10+26+12 = 48
Inopeki
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24
+24
----
48
anonymous
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and similarly
2x + 4
+ 2x + 4
__________
4x + 8
Inopeki
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Oh!
Give me another example?
anonymous
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\[(3x+5)+(4x+1)\]
Inopeki
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(3x+5)
+(4x+1)
--------
7x+6
anonymous
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that's it!
Inopeki
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Yes! :D Thanks