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- Nov 18th 2007, 06:52 AM #1xfactor0707Guest
## Need some help

Hi yall im new to this forum but im looking for some help.

Find all values of the variable for which the expression is undefined.

1) (4y)/( x- 3)

2) (4x + 12)/ (x^3 - 9x)

3) (7)/ (7 -x )

4) (2y)/ (y^2 - 6y - 7)

5) (7)/ (x^2 -4)

6)(4x)/ (2x - 1)

Can u please help or teach me how 2 do it

- Nov 18th 2007, 07:03 AM #2

- Nov 18th 2007, 07:51 AM #3
Much better!

We are looking for values of x where the expression is undefined. In the case of fractions we look for where the denominator is 0.

So for 1)

we know that is forbidden. Thus x = 3 is where the expression is undefined.

A more complicated example is number 4)

We are looking for places where

So y cannot be -1 or 7.

See what you can do with the rest.

-Dan