overtonka
Solve each system of equations by substitution
-3v-3x=15
5v+x=-29
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tkhunny
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Divide the first by 3 and something magic may pop out.
skullpatrol
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I tried to teach you this yesterday and you refused to learn?
overtonka
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I did not refuse I just didn't get it
tkhunny
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Well, @overtonka, I think @skullpatrol would be delighted to see you make a better effort, today.
Divide the first equation by 3 and show what you get.
overtonka
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-1v-1x=5
tkhunny
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Super! Any suggestion what we should do next?
Hint: I didn't have you divide by 3 just for fun.
overtonka
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solve for one of the variables?
skullpatrol
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Yes!
overtonka
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so 1v=5-1x?
skullpatrol
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Now what (hint: use the name of the method)
tkhunny
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Since we are using substitition, that would be the things to do.
Please abandon those silly-looking '1's. We don't usually write those unless we are trying to make a point.
overtonka
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ok
so v-x=5?
tkhunny
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No, why did you UNsolve? Please "solve for one of the variables".
overtonka
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v=5-x?
skullpatrol
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Correct.
overtonka
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so plug that in to the other equation?
skullpatrol
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Substitution principle:
An expression maybe replaced by another expression that has the same value
If $$a=b$$then b maybe substituted for a in any expression.
skullpatrol
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|dw:1362010398136:dw|
tkhunny
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It's your big chance. Let's see the substitution!