domain of rational function

[Guest]

Find the domain for the function:

3X^2-2X-7

This is what I did, sorry if I didn't display everything correctly:

2 + or - sqrt 2^2-4(3)(-7)/2(3)

2 + or - sqrt 88/6

I got 1 + or - sqrt 88/3 but the book found 1 + or - sqrt 22/3, how did they get this?

 

[Daniel_Feldman]

Hi.


Make sure you get your definitions straight.

The domain is the set of possible x values: in this case it is all real numbers.

What your are looking for are the zeros.

using quadratic formula:


2 +/- root(4-4(3)(-7))/6=2+/- root(88)/6



2+/- root(88)/6


now, we need to simplify root(88)

root(88)=root(4 x 22)=(2 +/- 2root(22))/6

=(1 +/- root(22))/3


is this clear?