Register to reply

Don't understand the graph of y^2=x^2

by SpaceKidd_N7
Tags: graph, y2x2
Share this thread:
Oct19-13, 10:10 PM
P: 6

I don't really understand the graph of y2=x2. 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!
Phys.Org News Partner Mathematics news on
'Moral victories' might spare you from losing again
Fair cake cutting gets its own algorithm
Effort to model Facebook yields key to famous math problem (and a prize)
Oct19-13, 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
Simon Bridge
Oct19-13, 10:29 PM
Sci Advisor
HW Helper
Simon Bridge's Avatar
P: 12,482
##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?

Oct19-13, 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!!
Oct20-13, 02:18 AM
P: 21,214
Quote Quote by Simon Bridge View Post
##y^2=x^2\Rightarrow y=\pm\sqrt{x^2}##

if ##y=+\sqrt{x^2} = |x|##

then ##y=-\sqrt{x^2}=\cdots##
Or this ...
If y2 = x2
then y2 - x2 = 0
so (y - x)(y + x) = 0
∴ y = x or y = -x

The graph of y2 = x2 looks like the union of the graphs of y = x and y = -x -- two straight lines.

Register to reply

Related Discussions
Plz help me understand this velocity time graph General Physics 2
Does amputated connected graph in Peskin's book is same as the irreducible graph? High Energy, Nuclear, Particle Physics 7
How to do velocity-time graph to distance graph/acceleration to velocity graph? Classical Physics 1
Manipulating inverse square graph into straight line graph Introductory Physics Homework 4
Complex numbers: don't understand graph of... 1/z General Math 4