If x+2y=2 and (x+y)2=9, what is the value of y?

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Monique
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Main Question or Discussion Point

If x+2y=2 and (x+y)2=9, what is the value of y?

And the answer is not -1.. what is the trick here that I'm missing? The answer is supposed to be 5.
 

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NateTG
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Monique said:
If x+2y=2 and (x+y)2=9, what is the value of y?

And the answer is not -1.. what is the trick here that I'm missing? The answer is supposed to be 5.
[tex]x+2y=2[/tex]
so
[tex]x=2-2y[/tex]
so
[tex](x+y)^2=(2-2y+y)^2=(2-y)^2=9[/tex]
square root of both sides:
[tex]\pm (2-y)=3[/tex]
[tex]-3=2-y[/tex] or [tex]3=2-y[/tex]
So the solutions (note the plural) are:
[tex](-8,5)[/tex] and [tex](4,-1)[/tex]

I'm guessing you forgot that every number has two square roots. ;)
 
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Monique
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ahhh see? these little simple things.. thanks NateTG!

I should be doing other things at 2 in the morning :grumpy:
 
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monique is a cutie :blush:
 

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