quadratic inequality

[oe39]

[ QUOTE ]


you get x < |3|, which is equivalent to saying -3 < x < 3

[/ QUOTE ]

this is not correct

|x| < 3 is equivalent to -3 < x < 3

[oe39]

[ QUOTE ]
hi,
dummy here. for whatever reason, i can't figure this out:

x^2-9<0

i broke it down as such:
(x-3)(x+3)<0
so:
x=3, x=-3


where do i go from here?

thanks,
dummy out.

[/ QUOTE ]

x^2 - 9 < 0

since x^2 = |x|^2,

|x|^2 < 9,

so |x| < 3, so -3 < x < 3

[gull]

Square roots are very confusing.

Remember that the square root IS NOT the inverse operation of the square. Math teachers in lower grades do a bad job of formally defining the sqare root, and that never gets cleared up for most people later in life.