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Don't understand the graph of y^2=x^2 
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#1
Oct1913, 10:10 PM

P: 6

Hi,
I don't really understand the graph of y^{2}=x^{2}. When I plot it in wolfram alpha, I get a plot that looks like an x or two diagonal intersecting lines that go through the origin. I can understand why there are points in the first, second, and fourth quadrants, but I am confused as to why there are points in the third quadrant. This isn't for any homework, I'm just trying to study for an exam. Thanks a lot! 


#2
Oct1913, 10:20 PM

P: 3

third quadrant  x < 0 and y < 0;
for some value a, x = a and y = a; x^2 = y^2 = a^2 


#3
Oct1913, 10:29 PM

Homework
Sci Advisor
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Thanks
P: 13,076

##y^2=x^2\Rightarrow y=\pm\sqrt{x^2}##
if ##y=+\sqrt{x^2} = x## then ##y=\sqrt{x^2}=\cdots## So what do you get if you plot both on the same axis? 


#4
Oct1913, 10:45 PM

P: 6

Don't understand the graph of y^2=x^2
Ohh okay, I totally get it now.
Thank you very much!! 


#5
Oct2013, 02:18 AM

Mentor
P: 21,399

If y^{2} = x^{2} then y^{2}  x^{2} = 0 so (y  x)(y + x) = 0 ∴ y = x or y = x The graph of y^{2} = x^{2} looks like the union of the graphs of y = x and y = x  two straight lines. 


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