Question

how to graph absolute value y=|x^2-9|

Answer 1

use a table of values to see whats happening .....

the curve will always be above or on the x-axis....

x: -5 -4 -3 -2 -1 0 1 2 3 4 5
y: 16 7 0


I'll let you finish the table... so you can see whats happening...

Answer 2

Basically, it would look like
\[y = x^2 - 9 \]
but the part that is negative in there is mirrored up to be positive.. that's the effect of the Absolute Value function.

To see by yourself, just take bunch of X values around 0, calculate Y values, mark it on paper and connect the lines, you'll get something close to the real thing.

However, computers are very handy in those stuff =]
Attached picture

Answer 3

there you go.... someone will always give the answer...

Answer 4

i <3 geogebra, it's useful =] (and open source!)
http://www.geogebra.org/
In this example, I just wrote down in the big input line on the bottom the following:
abs(x^2 - 9)
And hit enter hehe